diff --git a/backend/src/routes/admin.ts b/backend/src/routes/admin.ts
index c4e4fc6..c2e2037 100644
--- a/backend/src/routes/admin.ts
+++ b/backend/src/routes/admin.ts
@@ -5,7 +5,7 @@ import { eq, desc } from 'drizzle-orm';
 import { v4 as uuid } from 'uuid';
 import bcrypt from 'bcrypt';
 import { db } from '../db/index';
-import { users, authorMappings, syncLogs, projects, projectRepos, gitCommits, gitPRs, userProjectPermissions } from '../db/schema';
+import { users, authorMappings, syncLogs, projects, projectRepos, gitCommits, gitPRs, userProjectPermissions, objectives, keyResults, krLogs } from '../db/schema';
 import { requireRole } from '../middleware/role';
 import { AppError } from '../middleware/error-handler';
 
@@ -178,6 +178,17 @@ adminRoutes.patch('/admin/projects/:id', zValidator('json', updateProjectSchema)
 
 adminRoutes.delete('/admin/projects/:id', async (c) => {
   const id = c.req.param('id');
+  await db.delete(userProjectPermissions).where(eq(userProjectPermissions.projectId, id));
+  await db.delete(projectRepos).where(eq(projectRepos.projectId, id));
+  const objs = await db.select().from(objectives).where(eq(objectives.projectId, id));
+  for (const obj of objs) {
+    const krs = await db.select().from(keyResults).where(eq(keyResults.objectiveId, obj.id));
+    for (const kr of krs) {
+      await db.delete(krLogs).where(eq(krLogs.krId, kr.id));
+    }
+    await db.delete(keyResults).where(eq(keyResults.objectiveId, obj.id));
+  }
+  await db.delete(objectives).where(eq(objectives.projectId, id));
   await db.delete(projects).where(eq(projects.id, id));
   return c.json({ code: 0, data: null, message: 'success' });
 });
diff --git a/backend/src/routes/projects.ts b/backend/src/routes/projects.ts
index 4f456fb..6a164d7 100644
--- a/backend/src/routes/projects.ts
+++ b/backend/src/routes/projects.ts
@@ -76,6 +76,19 @@ projectRoutes.delete('/projects/:id',
   requireRole('admin'),
   async (c) => {
     const id = c.req.param('id');
+    // 先清理关联数据（外键约束）
+    await db.delete(userProjectPermissions).where(eq(userProjectPermissions.projectId, id));
+    await db.delete(projectRepos).where(eq(projectRepos.projectId, id));
+    // 清理 OKR：KR logs → KR → Objectives
+    const objs = await db.select().from(objectives).where(eq(objectives.projectId, id));
+    for (const obj of objs) {
+      const krs = await db.select().from(keyResults).where(eq(keyResults.objectiveId, obj.id));
+      for (const kr of krs) {
+        await db.delete(krLogs).where(eq(krLogs.krId, kr.id));
+      }
+      await db.delete(keyResults).where(eq(keyResults.objectiveId, obj.id));
+    }
+    await db.delete(objectives).where(eq(objectives.projectId, id));
     await db.delete(projects).where(eq(projects.id, id));
     return c.json({ code: 0, data: null, message: 'success' });
   }