diff --git a/apps/api/src/services/telegram_gateway.py b/apps/api/src/services/telegram_gateway.py
index c356cf5a..3d405e20 100644
--- a/apps/api/src/services/telegram_gateway.py
+++ b/apps/api/src/services/telegram_gateway.py
@@ -157,8 +157,13 @@ class TelegramMessage:
         else:
             conf_emoji = "🔴"
 
-        # 自動生成事件編號
-        incident_id = self.incident_id or f"INC-{self.approval_id[:8].upper()}"
+        # 自動生成事件編號 (2026-03-26 修復: 檢查是否已有 INC- 前綴)
+        if self.incident_id:
+            incident_id = self.incident_id
+        elif self.approval_id.upper().startswith("INC-"):
+            incident_id = self.approval_id.upper()
+        else:
+            incident_id = f"INC-{self.approval_id[:8].upper()}"
 
         # SignOz URL (優先使用動態 URL) - 必須 HTML 轉義防止解析錯誤
         service_name = self.resource_name.split("-")[0] if "-" in self.resource_name else self.resource_name