diff --git a/api.py b/api.py
index 9cfd319..3c19447 100644
--- a/api.py
+++ b/api.py
@@ -25,7 +25,7 @@ from fastapi.responses import FileResponse, JSONResponse
 
 from db import ServerDB
 from receiver import Receiver, ReceiverError
-from settings import STORAGE_ROOT, TMP_ROOT, TOKEN
+from settings import QUOTA_BYTES, STORAGE_ROOT, TMP_ROOT, TOKEN
 from storage import Storage
 from task_manager import TaskManager
 
@@ -63,6 +63,19 @@ async def list_files():
     return {"files": db.list_files()}
 
 
+@app.get("/api/quota", dependencies=[Depends(verify_token)])
+async def quota():
+    """用户空间配额: 已用 (files size 总和) / 配额 / 剩余"""
+    used = db.sum_files_size()
+    remain = max(QUOTA_BYTES - used, 0)
+    return {
+        "used_bytes": used,
+        "quota_bytes": QUOTA_BYTES,
+        "remain_bytes": remain,
+        "percent": round(used * 100 / QUOTA_BYTES, 1) if QUOTA_BYTES else 0,
+    }
+
+
 @app.delete("/api/files/{file_id}", dependencies=[Depends(verify_token)])
 async def delete_file(file_id: str):
     """删除文件 (卷目录 + 入库记录)"""
diff --git a/db.py b/db.py
index bacd781..ee4ec25 100644
--- a/db.py
+++ b/db.py
@@ -201,6 +201,12 @@ class ServerDB:
             cur = conn.execute("DELETE FROM files WHERE file_id = ?", (file_id,))
             return cur.rowcount > 0
 
+    def sum_files_size(self) -> int:
+        """全部文件 size 总和 (配额统计用)"""
+        with self._conn() as conn:
+            row = conn.execute("SELECT COALESCE(SUM(size), 0) FROM files").fetchone()
+        return int(row[0])
+
     def get_file(self, file_id: str) -> dict[str, Any] | None:
         """单文件记录 (下载端点, 含解密参数 enc_params + 卷数)"""
         with self._conn() as conn:
diff --git a/settings.py b/settings.py
index 15196f5..19c9b5c 100644
--- a/settings.py
+++ b/settings.py
@@ -17,6 +17,9 @@ STORAGE_ROOT = Path(os.environ.get("SZ_STORAGE_ROOT", "data/storage"))
 # 临时目录 (分卷/合并中间产物)
 TMP_ROOT = Path(os.environ.get("SZ_TMP_ROOT", "data/tmp"))
 
+# 用户空间配额 (已用 = files 表 size 总和, 超配额拒绝新上传? 暂只读展示)
+QUOTA_BYTES = int(os.environ.get("SZ_QUOTA", str(10 * 1024**3)))  # 默认 10GB
+
 # API 服务
 HOST = os.environ.get("SZ_HOST", "0.0.0.0")
 PORT = int(os.environ.get("SZ_PORT", "8000"))
diff --git a/tests/test_api.py b/tests/test_api.py
index b92c22c..33954f2 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -237,6 +237,16 @@ class ServerPipelineTest(unittest.TestCase):
             len(self.client.get("/api/files", headers=AUTH).json()["files"]), before
         )
 
+        # 配额: 返回结构 + 已用 = files size 总和
+        r = self.client.get("/api/quota", headers=AUTH)
+        self.assertEqual(r.status_code, 200)
+        q = r.json()
+        self.assertIn("used_bytes", q)
+        self.assertIn("quota_bytes", q)
+        self.assertIn("remain_bytes", q)
+        self.assertEqual(q["used_bytes"], q["quota_bytes"] - q["remain_bytes"])
+        self.assertGreater(q["quota_bytes"], 0)
+
         # del: 删除后列表减少, 再删 404
         r = self.client.delete(f"/api/files/{file_id}", headers=AUTH)
         self.assertEqual(r.status_code, 200, r.text)