diff --git a/apps/api/src/services/decision_manager.py b/apps/api/src/services/decision_manager.py
index 5209ec44..51d643c8 100644
--- a/apps/api/src/services/decision_manager.py
+++ b/apps/api/src/services/decision_manager.py
@@ -353,7 +353,7 @@ async def _push_decision_to_telegram(
                 approval_id=approval_id,
                 risk_level=risk_level,
                 resource_name=target[:50],
-                root_cause=reasoning[:300] if reasoning else description[:300],
+                root_cause=reasoning[:500] if reasoning else description[:500],
                 suggested_action=action[:120] if action else (description[:120] if description else "待分析"),
                 estimated_downtime="5-15 min",
                 primary_responsibility="INFRA",