diff --git a/backend/app/api/settings.py b/backend/app/api/settings.py
index 7f31977..bb3af65 100644
--- a/backend/app/api/settings.py
+++ b/backend/app/api/settings.py
@@ -1486,7 +1486,7 @@ def update_quote_interval(req: QuoteIntervalIn, request: Request) -> dict:
     """更新行情轮询间隔。按档位自动 clamp。"""
     qs = getattr(request.app.state, "quote_service", None)
     if not qs:
-        return {"interval": req.interval, "min_interval": qs.get_min_interval(), "max_interval": 60.0}
+        return {"interval": req.interval, "min_interval": 6.0, "max_interval": 60.0}
     clamped = qs.set_interval(req.interval)
     return {
         "interval": clamped,
diff --git a/backend/tests/test_quote_interval_settings.py b/backend/tests/test_quote_interval_settings.py
new file mode 100644
index 0000000..b717c78
--- /dev/null
+++ b/backend/tests/test_quote_interval_settings.py
@@ -0,0 +1,29 @@
+"""行情轮询间隔接口: quote_service 缺失时的兜底分支不能抛 AttributeError (issue #261)。"""
+
+from __future__ import annotations
+
+from types import SimpleNamespace
+
+from app.api.settings import QuoteIntervalIn, update_quote_interval
+
+
+def _request_without_quote_service() -> SimpleNamespace:
+    return SimpleNamespace(app=SimpleNamespace(state=SimpleNamespace(quote_service=None)))
+
+
+def test_update_quote_interval_without_service_returns_defaults():
+    result = update_quote_interval(
+        QuoteIntervalIn(interval=6.0), request=_request_without_quote_service()
+    )
+
+    assert result == {"interval": 6.0, "min_interval": 6.0, "max_interval": 60.0}
+
+
+def test_update_quote_interval_without_service_keeps_requested_interval():
+    result = update_quote_interval(
+        QuoteIntervalIn(interval=12.0), request=_request_without_quote_service()
+    )
+
+    assert result["interval"] == 12.0
+    assert result["min_interval"] == 6.0
+    assert result["max_interval"] == 60.0