diff --git a/media_platform/bilibili/core.py b/media_platform/bilibili/core.py
index a2c4068..b34cfde 100644
--- a/media_platform/bilibili/core.py
+++ b/media_platform/bilibili/core.py
@@ -24,6 +24,7 @@
 
 import asyncio
 import os
+import sys
 # import random  # Removed as we now use fixed config.CRAWLER_MAX_SLEEP_SEC intervals
 from asyncio import Task
 from typing import Dict, List, Optional, Tuple, Union
@@ -113,6 +114,15 @@ class BilibiliCrawler(AbstractCrawler):
                     browser_context=self.browser_context,
                     urls=self.cookie_urls,
                 )
+                # 登录流程结束后再校验一次，宁可在这里失败也不要带着未登录状态跑完全程：
+                # B 站的清晰度由 playurl 依据 Cookie 决定，死会话不会报错，
+                # 只会把带 get_media 的视频静默限制在 480P
+                if not await self.bili_client.pong():
+                    utils.logger.error(
+                        "[BilibiliCrawler.start] 登录流程结束后仍未登录：请确认扫码已完成、"
+                        "或 config.COOKIES 是否有效。已终止，否则视频会被静默限制在 480P。"
+                    )
+                    sys.exit(1)
 
             crawler_type_var.set(config.CRAWLER_TYPE)
             if config.CRAWLER_TYPE == "search":
diff --git a/media_platform/bilibili/login.py b/media_platform/bilibili/login.py
index bb19af5..13e31a1 100644
--- a/media_platform/bilibili/login.py
+++ b/media_platform/bilibili/login.py
@@ -48,6 +48,18 @@ LOGIN_ENTRY_SELECTORS = [
 ]
 
 
+def is_login_cookie_refreshed(cookie_dict: dict, sessdata_before_login: str) -> bool:
+    """判断浏览器里的 SESSDATA 是否已经是扫码换发后的新值。
+
+    过期的 SESSDATA 同样会留在浏览器里，所以"cookie 存在"不等于"已登录"。
+    只判断存在会把死会话判成登录成功：既跳过扫码，又把这份死 cookie 灌给
+    API client —— B 站 playurl 依据 Cookie 决定清晰度，结果是详情和评论照常拿到
+    （这两个接口不要求登录），视频却被静默限制在 480P。
+    """
+    sessdata = cookie_dict.get("SESSDATA", "")
+    return bool(sessdata) and sessdata != sessdata_before_login
+
+
 class BilibiliLogin(AbstractLogin):
     def __init__(self,
                  login_type: str,
@@ -61,6 +73,8 @@ class BilibiliLogin(AbstractLogin):
         self.context_page = context_page
         self.login_phone = login_phone
         self.cookie_str = cookie_str
+        # 进入登录流程前浏览器里已有的 SESSDATA，用于区分"cookie 存在"与"cookie 有效"
+        self._sessdata_before_login: str = ""
 
     async def begin(self):
         """Start login bilibili"""
@@ -79,19 +93,27 @@ class BilibiliLogin(AbstractLogin):
     async def check_login_state(self) -> bool:
         """
             Check if the current login status is successful and return True otherwise return False
-            retry decorator will retry 20 times if the return value is False, and the retry interval is 1 second
+            retry decorator will retry 600 times if the return value is False, and the retry interval is 1 second
             if max retry times reached, raise RetryError
         """
         current_cookie = await self.browser_context.cookies()
         _, cookie_dict = utils.convert_cookies(current_cookie)
-        if cookie_dict.get("SESSDATA", "") or cookie_dict.get("DedeUserID"):
-            return True
-        return False
+        return is_login_cookie_refreshed(cookie_dict, self._sessdata_before_login)
 
     async def login_by_qrcode(self):
         """login bilibili website and keep webdriver login state"""
         utils.logger.info("[BilibiliLogin.login_by_qrcode] Begin login bilibili by qrcode ...")
 
+        # 记下扫码前的 SESSDATA：扫码成功后它会被换发成新值，
+        # check_login_state 靠这个差值判断"真的登录了"而不是"只剩一份过期 cookie"
+        _, cookie_dict = utils.convert_cookies(await self.browser_context.cookies())
+        self._sessdata_before_login = cookie_dict.get("SESSDATA", "")
+        if self._sessdata_before_login:
+            utils.logger.warning(
+                "[BilibiliLogin.login_by_qrcode] 浏览器中残留了 SESSDATA，但接口校验为未登录，"
+                "该会话已失效；本次必须重新扫码换发新 cookie 才会继续 ..."
+            )
+
         # click login button
         login_entry_selector = ", ".join(LOGIN_ENTRY_SELECTORS)
         try:
diff --git a/tests/test_bilibili_login_state.py b/tests/test_bilibili_login_state.py
new file mode 100644
index 0000000..9c8fe24
--- /dev/null
+++ b/tests/test_bilibili_login_state.py
@@ -0,0 +1,46 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) 2025 relakkes@gmail.com
+#
+# This file is part of MediaCrawler project.
+# Repository: https://github.com/NanmiCoder/MediaCrawler/blob/main/tests/test_bilibili_login_state.py
+# GitHub: https://github.com/NanmiCoder
+# Licensed under NON-COMMERCIAL LEARNING LICENSE 1.1
+#
+
+"""B 站登录态判定的回归测试。
+
+回归背景：``check_login_state`` 曾经只判断 SESSDATA **是否存在**。当浏览器里
+残留一份过期 SESSDATA 时（B 站不会主动清掉它），流程会被判成"登录成功"：
+既跳过扫码，又把这份死 cookie 灌给 API client。后果是详情和评论照常爬到
+（这两个接口不要求登录），但 playurl 依据 Cookie 定清晰度，视频被静默限制在 480P。
+
+这里只测判定逻辑本身，不启浏览器、不发网络请求。
+"""
+
+from __future__ import annotations
+
+from media_platform.bilibili.login import is_login_cookie_refreshed
+
+STALE = "sessdata-remaining-from-expired-session"
+FRESH = "sessdata-reissued-by-qrcode-scan"
+
+
+def test_stale_sessdata_is_not_treated_as_logged_in() -> None:
+    """残留的过期 SESSDATA 不能算登录成功（本次回归的核心）"""
+    assert is_login_cookie_refreshed({"SESSDATA": STALE}, STALE) is False
+
+
+def test_absent_sessdata_is_not_logged_in() -> None:
+    """完全没有 SESSDATA 时未登录；只有 DedeUserID 不足以证明会话有效"""
+    assert is_login_cookie_refreshed({}, "") is False
+    assert is_login_cookie_refreshed({"DedeUserID": "434377496"}, "") is False
+
+
+def test_refreshed_sessdata_is_logged_in() -> None:
+    """扫码换发成新值之后才放行"""
+    assert is_login_cookie_refreshed({"SESSDATA": FRESH}, STALE) is True
+
+
+def test_sessdata_appearing_from_nothing_is_logged_in() -> None:
+    """本来就没有 SESSDATA（真未登录）时，扫码写进来的任意值都算成功"""
+    assert is_login_cookie_refreshed({"SESSDATA": FRESH}, "") is True