diff --git a/web/src/api/workspaces.ts b/web/src/api/workspaces.ts
index c643fed..b2a8869 100644
--- a/web/src/api/workspaces.ts
+++ b/web/src/api/workspaces.ts
@@ -52,6 +52,11 @@ export const workspacesApi = {
   release: (wtID: string) =>
     request<Worktree>(`/api/v1/worktrees/${enc(wtID)}/release`, { method: 'POST' }),
 
+  listBranches(wsID: string): Promise<string[]> {
+    return request<{ branches: string[] }>(`/api/v1/workspaces/${enc(wsID)}/branches`)
+      .then(r => r.branches)
+  },
+
   // ===== Git ops =====
   statusOnMain: (wsID: string) =>
     request<FileStatus[]>(`/api/v1/workspaces/${enc(wsID)}/main/status`),
diff --git a/web/src/views/workspaces/components/WorktreesTab.vue b/web/src/views/workspaces/components/WorktreesTab.vue
index d432f85..e0093d9 100644
--- a/web/src/views/workspaces/components/WorktreesTab.vue
+++ b/web/src/views/workspaces/components/WorktreesTab.vue
@@ -6,7 +6,7 @@
     >
       <NButton
         type="primary"
-        @click="showCreate = true"
+        @click="openCreate"
       >
         新建 worktree
       </NButton>
@@ -31,7 +31,13 @@
           <NInput v-model:value="newBranch" />
         </NFormItem>
         <NFormItem label="基线分支（默认 default_branch）">
-          <NInput v-model:value="newBase" />
+          <NSelect
+            v-model:value="newBase"
+            :options="baseBranchOptions"
+            :loading="branchesLoading"
+            clearable
+            placeholder="默认使用 default_branch"
+          />
         </NFormItem>
       </NForm>
       <template #footer>
@@ -71,11 +77,13 @@ import {
   NForm,
   NFormItem,
   NInput,
+  NSelect,
   useMessage,
   useDialog,
 } from 'naive-ui'
 import type { DataTableColumns } from 'naive-ui'
 import { useWorkspacesStore } from '@/stores/workspaces'
+import { workspacesApi } from '@/api/workspaces'
 import CommitDialog from './CommitDialog.vue'
 import type { Workspace, Worktree, WorktreeStatus } from '@/api/types'
 
@@ -87,16 +95,40 @@ const dialog = useDialog()
 const showCreate = ref<boolean>(false)
 const creating = ref<boolean>(false)
 const newBranch = ref<string>('')
-const newBase = ref<string>('')
+const newBase = ref<string | null>(null)
 
 const commitFor = ref<Worktree | null>(null)
 
+// Branch list for base_branch selector
+const branches = ref<string[]>([])
+const branchesLoading = ref(false)
+
 const STATUS_TAG_TYPE: Record<WorktreeStatus, 'warning' | 'error' | 'default'> = {
   active: 'warning',
   pruning: 'error',
   idle: 'default',
 }
 
+async function openCreate() {
+  showCreate.value = true
+  newBranch.value = ''
+  newBase.value = null
+  // Fetch branch list when dialog opens
+  branchesLoading.value = true
+  try {
+    branches.value = await workspacesApi.listBranches(props.ws.id)
+  } catch {
+    // Silently fail — user can still type manually
+    branches.value = []
+  } finally {
+    branchesLoading.value = false
+  }
+}
+
+const baseBranchOptions = computed(() =>
+  branches.value.map((b) => ({ label: b, value: b })),
+)
+
 async function onCreate() {
   if (!newBranch.value.trim()) {
     msg.error('分支名为必填')
@@ -110,7 +142,7 @@ async function onCreate() {
     })
     showCreate.value = false
     newBranch.value = ''
-    newBase.value = ''
+    newBase.value = null
   } catch (e: unknown) {
     msg.error('创建失败：' + (e instanceof Error ? e.message : String(e)))
   } finally {