diff --git a/src/zotero_kb/templates/index.html b/src/zotero_kb/templates/index.html
index 9e7c257..00760b4 100644
--- a/src/zotero_kb/templates/index.html
+++ b/src/zotero_kb/templates/index.html
@@ -380,12 +380,43 @@
 
     <script>
       const ABSTRACT_PREVIEW_DELAY_MS = 3000;
+      const IMPORT_SESSION_STORAGE_KEY = "zotero-kb.import-modal";
+
+      function readImportSessionState() {
+        try {
+          const raw = window.sessionStorage.getItem(IMPORT_SESSION_STORAGE_KEY);
+          if (!raw) {
+            return {};
+          }
+          const payload = JSON.parse(raw);
+          return typeof payload === "object" && payload ? payload : {};
+        } catch (_error) {
+          return {};
+        }
+      }
+
+      const importSessionState = readImportSessionState();
 
       const state = {
         projects: [],
         currentProjectId: null,
         currentCards: [],
+        collectionTree: [],
         isImportModalOpen: false,
+        selectedCollectionKey: typeof importSessionState.selectedCollectionKey === "string"
+          ? importSessionState.selectedCollectionKey
+          : null,
+        expandedCollectionKeys: new Set(
+          Array.isArray(importSessionState.expandedCollectionKeys)
+            ? importSessionState.expandedCollectionKeys.filter((value) => typeof value === "string")
+            : []
+        ),
+        selectedItemKeys: new Set(
+          Array.isArray(importSessionState.selectedItemKeys)
+            ? importSessionState.selectedItemKeys.filter((value) => typeof value === "string")
+            : []
+        ),
+        visibleCollectionItems: [],
       };
 
       const elements = {
@@ -396,6 +427,15 @@
         importModalOverlay: document.getElementById("import-modal-overlay"),
         openImportModalButton: document.getElementById("open-import-modal-button"),
         closeImportModalButton: document.getElementById("close-import-modal-button"),
+        importModalProjectLabel: document.getElementById("import-modal-project-label"),
+        collectionStatus: document.getElementById("collection-status"),
+        collectionTree: document.getElementById("modal-collection-tree"),
+        collectionItems: document.getElementById("modal-collection-items"),
+        selectedCount: document.getElementById("modal-selected-count"),
+        selectDescendantsButton: document.getElementById("modal-select-descendants-button"),
+        clearSelectionButton: document.getElementById("modal-clear-selection-button"),
+        importSelectedItemsButton: document.getElementById("modal-import-selected-items-button"),
+        previewPopover: document.getElementById("item-preview-popover"),
         currentProjectLabel: document.getElementById("current-project-label"),
         cardList: document.getElementById("card-list"),
         cardDetail: document.getElementById("card-detail"),
@@ -413,6 +453,17 @@
         planPanel: document.getElementById("plan-panel"),
       };
 
+      function persistImportSessionState() {
+        window.sessionStorage.setItem(
+          IMPORT_SESSION_STORAGE_KEY,
+          JSON.stringify({
+            selectedCollectionKey: state.selectedCollectionKey,
+            expandedCollectionKeys: Array.from(state.expandedCollectionKeys),
+            selectedItemKeys: Array.from(state.selectedItemKeys),
+          })
+        );
+      }
+
       function setStatus(target, message, isError = false) {
         target.textContent = message || "";
         target.classList.toggle("error", Boolean(isError));
@@ -527,37 +578,285 @@
         `).join("");
       }
 
-      function syncImportModalVisibility() {
-        elements.importModal.hidden = !state.isImportModalOpen;
-        elements.importModal.setAttribute("aria-hidden", state.isImportModalOpen ? "false" : "true");
-        document.body.classList.toggle("modal-open", state.isImportModalOpen);
+      function renderSelectedCount() {
+        elements.selectedCount.textContent = `已选 ${state.selectedItemKeys.size} 篇`;
       }
 
-      function openImportModal() {
+      function updateImportActionState() {
+        const hasProject = Boolean(state.currentProjectId);
+        const hasSelection = state.selectedItemKeys.size > 0;
+        elements.importModalProjectLabel.textContent = hasProject ? `当前项目：${state.currentProjectId}` : "未选择项目";
+        elements.importSelectedItemsButton.disabled = !hasProject || !hasSelection;
+        elements.importSelectedItemsButton.title = !hasProject ? "请先选择项目" : (hasSelection ? "" : "请先选择文献");
+        elements.selectDescendantsButton.disabled = !state.visibleCollectionItems.length;
+        elements.clearSelectionButton.disabled = !state.selectedItemKeys.size;
+        renderSelectedCount();
+      }
+
+      function collectCollectionParents(nodes, parentKey = null, lookup = new Map()) {
+        for (const node of nodes) {
+          lookup.set(node.collection_key, parentKey);
+          collectCollectionParents(node.children || [], node.collection_key, lookup);
+        }
+        return lookup;
+      }
+
+      function ensureSelectedCollectionExpanded() {
+        if (!state.selectedCollectionKey) {
+          return;
+        }
+        const parentLookup = collectCollectionParents(state.collectionTree);
+        let currentKey = parentLookup.get(state.selectedCollectionKey) || null;
+        while (currentKey) {
+          state.expandedCollectionKeys.add(currentKey);
+          currentKey = parentLookup.get(currentKey) || null;
+        }
+      }
+
+      function renderCollectionTree() {
+        if (!state.collectionTree.length) {
+          elements.collectionTree.innerHTML = '<div class="empty">暂无 collection。</div>';
+          return;
+        }
+
+        elements.collectionTree.innerHTML = "";
+        const fragment = document.createDocumentFragment();
+
+        function appendNode(node, depth) {
+          const wrapper = document.createElement("div");
+          wrapper.style.display = "grid";
+          wrapper.style.gap = "0.35rem";
+          wrapper.style.marginLeft = `${depth * 0.9}rem`;
+
+          const row = document.createElement("div");
+          row.className = "row";
+          row.style.alignItems = "stretch";
+          row.style.gap = "0.45rem";
+
+          const hasChildren = Array.isArray(node.children) && node.children.length > 0;
+          if (hasChildren) {
+            const toggle = document.createElement("button");
+            toggle.type = "button";
+            toggle.className = "secondary";
+            toggle.style.flex = "0 0 auto";
+            toggle.style.width = "auto";
+            toggle.style.padding = "0.55rem 0.75rem";
+            toggle.textContent = state.expandedCollectionKeys.has(node.collection_key) ? "−" : "+";
+            toggle.addEventListener("click", () => {
+              if (state.expandedCollectionKeys.has(node.collection_key)) {
+                state.expandedCollectionKeys.delete(node.collection_key);
+              } else {
+                state.expandedCollectionKeys.add(node.collection_key);
+              }
+              persistImportSessionState();
+              renderCollectionTree();
+            });
+            row.appendChild(toggle);
+          }
+
+          const button = document.createElement("button");
+          button.type = "button";
+          button.className = "project-item" + (node.collection_key === state.selectedCollectionKey ? " active" : "");
+          button.style.textAlign = "left";
+          button.innerHTML = `
+            <strong>${node.name}</strong>
+            <div class="meta">${node.direct_item_count} 篇直接文献 · ${node.descendant_item_count} 篇含子目录</div>
+          `;
+          button.addEventListener("click", () => {
+            loadCollectionItems(node.collection_key).catch((error) => {
+              setStatus(elements.collectionStatus, error.message, true);
+            });
+          });
+          row.appendChild(button);
+          wrapper.appendChild(row);
+          fragment.appendChild(wrapper);
+
+          if (hasChildren && state.expandedCollectionKeys.has(node.collection_key)) {
+            for (const child of node.children) {
+              appendNode(child, depth + 1);
+            }
+          }
+        }
+
+        for (const node of state.collectionTree) {
+          appendNode(node, 0);
+        }
+        elements.collectionTree.appendChild(fragment);
+      }
+
+      function renderCollectionItems() {
+        if (!state.selectedCollectionKey) {
+          elements.collectionItems.innerHTML = '<div class="empty">先选择一个 collection。</div>';
+          updateImportActionState();
+          return;
+        }
+        if (!state.visibleCollectionItems.length) {
+          elements.collectionItems.innerHTML = '<div class="empty">当前目录及子目录下没有可导入文献。</div>';
+          updateImportActionState();
+          return;
+        }
+
+        elements.collectionItems.innerHTML = "";
+        for (const item of state.visibleCollectionItems) {
+          const row = document.createElement("label");
+          row.className = "project-item";
+          row.style.display = "grid";
+          row.style.gridTemplateColumns = "auto 1fr";
+          row.style.gap = "0.75rem";
+          row.style.alignItems = "start";
+          row.innerHTML = `
+            <input type="checkbox" ${state.selectedItemKeys.has(item.item_key) ? "checked" : ""} />
+            <div>
+              <strong>${item.title}</strong>
+              <div class="meta">${item.item_key} · ${item.year || "-"} · ${item.item_type || "-"}</div>
+              <p>${item.abstract || "暂无摘要"}</p>
+            </div>
+          `;
+          row.querySelector("input").addEventListener("change", () => toggleItemSelection(item.item_key));
+          elements.collectionItems.appendChild(row);
+        }
+        updateImportActionState();
+      }
+
+      async function loadCollectionTree() {
+        setStatus(elements.collectionStatus, "正在加载 collection...");
+        const payload = await api("/api/zotero/collections/tree");
+        state.collectionTree = Array.isArray(payload.collections) ? payload.collections : [];
+        if (!state.selectedCollectionKey && state.collectionTree.length) {
+          state.selectedCollectionKey = state.collectionTree[0].collection_key;
+        }
+        ensureSelectedCollectionExpanded();
+        persistImportSessionState();
+        renderCollectionTree();
+        if (state.selectedCollectionKey) {
+          await loadCollectionItems(state.selectedCollectionKey);
+          return;
+        }
+        state.visibleCollectionItems = [];
+        renderCollectionItems();
+        setStatus(elements.collectionStatus, "");
+      }
+
+      async function loadCollectionItems(collectionKey) {
+        state.selectedCollectionKey = collectionKey;
+        ensureSelectedCollectionExpanded();
+        persistImportSessionState();
+        renderCollectionTree();
+        setStatus(elements.collectionStatus, "正在加载文献...");
+        const payload = await api(`/api/zotero/collections/${collectionKey}/items`);
+        state.visibleCollectionItems = Array.isArray(payload.items) ? payload.items : [];
+        renderCollectionItems();
+        const visibleCount = state.visibleCollectionItems.length;
+        setStatus(
+          elements.collectionStatus,
+          visibleCount ? `当前目录及子目录共 ${visibleCount} 篇文献。` : "当前目录及子目录下没有可导入文献。"
+        );
+      }
+
+      function toggleItemSelection(itemKey) {
+        if (state.selectedItemKeys.has(itemKey)) {
+          state.selectedItemKeys.delete(itemKey);
+        } else {
+          state.selectedItemKeys.add(itemKey);
+        }
+        persistImportSessionState();
+        renderCollectionItems();
+        updateImportActionState();
+      }
+
+      function selectVisibleItems() {
+        for (const item of state.visibleCollectionItems) {
+          state.selectedItemKeys.add(item.item_key);
+        }
+        persistImportSessionState();
+        renderCollectionItems();
+        updateImportActionState();
+      }
+
+      function clearSelectedItems() {
+        state.selectedItemKeys.clear();
+        persistImportSessionState();
+        renderCollectionItems();
+        updateImportActionState();
+      }
+
+      async function importSelectedItems() {
+        if (!state.currentProjectId || !state.selectedItemKeys.size) {
+          updateImportActionState();
+          return;
+        }
+        setStatus(elements.collectionStatus, "正在导入...");
+        const payload = await api(`/api/projects/${state.currentProjectId}/imports/item-keys`, {
+          method: "POST",
+          body: JSON.stringify({ item_keys: Array.from(state.selectedItemKeys) }),
+        });
+        state.selectedItemKeys.clear();
+        persistImportSessionState();
+        renderCollectionItems();
+        renderCards(payload.project_view?.cards || []);
+        setStatus(elements.collectionStatus, "导入完成。");
+        updateImportActionState();
+        closeImportModal();
+      }
+
+      async function openImportModal() {
         state.isImportModalOpen = true;
-        syncImportModalVisibility();
+        elements.importModal.hidden = false;
+        elements.importModal.setAttribute("aria-hidden", "false");
+        document.body.classList.toggle("modal-open", true);
+        elements.previewPopover.hidden = true;
+        elements.previewPopover.textContent = "";
+        updateImportActionState();
+        if (!state.collectionTree.length) {
+          try {
+            await loadCollectionTree();
+          } catch (error) {
+            setStatus(elements.collectionStatus, error.message, true);
+          }
+        } else if (state.selectedCollectionKey && !state.visibleCollectionItems.length) {
+          try {
+            await loadCollectionItems(state.selectedCollectionKey);
+          } catch (error) {
+            setStatus(elements.collectionStatus, error.message, true);
+          }
+        } else {
+          renderCollectionTree();
+          renderCollectionItems();
+        }
       }
 
       function closeImportModal() {
         state.isImportModalOpen = false;
-        syncImportModalVisibility();
+        elements.importModal.hidden = true;
+        elements.importModal.setAttribute("aria-hidden", "true");
+        document.body.classList.toggle("modal-open", false);
+        elements.previewPopover.hidden = true;
+        elements.previewPopover.textContent = "";
       }
 
       async function loadProjects() {
         const projects = await api("/api/projects");
         state.projects = projects;
+        if (state.currentProjectId && !projects.some((project) => project.id === state.currentProjectId)) {
+          state.currentProjectId = projects.length ? projects[0].id : null;
+        }
         if (!state.currentProjectId && projects.length) {
           state.currentProjectId = projects[0].id;
         }
         renderProjects();
+        updateImportActionState();
         if (state.currentProjectId) {
           await selectProject(state.currentProjectId, false);
+          return;
         }
+        elements.currentProjectLabel.textContent = "当前未选择项目。";
+        renderCards([]);
       }
 
       async function selectProject(projectId, rerender = true) {
         state.currentProjectId = projectId;
         elements.currentProjectLabel.textContent = `当前项目：${projectId}`;
+        updateImportActionState();
         if (rerender) {
           renderProjects();
         }
@@ -600,9 +899,18 @@
 
       elements.refreshProjectsButton.addEventListener("click", loadProjects);
 
-      elements.openImportModalButton.addEventListener("click", openImportModal);
+      elements.openImportModalButton.addEventListener("click", () => {
+        openImportModal();
+      });
       elements.closeImportModalButton.addEventListener("click", closeImportModal);
       elements.importModalOverlay.addEventListener("click", closeImportModal);
+      elements.selectDescendantsButton.addEventListener("click", selectVisibleItems);
+      elements.clearSelectionButton.addEventListener("click", clearSelectedItems);
+      elements.importSelectedItemsButton.addEventListener("click", () => {
+        importSelectedItems().catch((error) => {
+          setStatus(elements.collectionStatus, error.message, true);
+        });
+      });
       document.addEventListener("keydown", (event) => {
         if (event.key === "Escape" && state.isImportModalOpen) {
           closeImportModal();
@@ -660,7 +968,8 @@
       elements.recommendTab.addEventListener("click", () => activateTab("recommend"));
       elements.planTab.addEventListener("click", () => activateTab("plan"));
 
-      syncImportModalVisibility();
+      closeImportModal();
+      updateImportActionState();
       loadProjects().catch((error) => {
         setStatus(elements.projectStatus, error.message, true);
       });
diff --git a/tests/test_ui.py b/tests/test_ui.py
index 0313c0e..ee2ff68 100644
--- a/tests/test_ui.py
+++ b/tests/test_ui.py
@@ -41,3 +41,7 @@ def test_index_contains_import_modal_controls(tmp_path) -> None:
     assert 'id="item-preview-popover"' in html
     assert 'const ABSTRACT_PREVIEW_DELAY_MS = 3000;' in html
     assert 'isImportModalOpen: false' in html
+    assert "function openImportModal()" in html
+    assert "function closeImportModal()" in html
+    assert "function updateImportActionState()" in html
+    assert 'document.body.classList.toggle("modal-open"' in html