diff --git a/backend/mpc-system/services/service-party-app/electron/main.ts b/backend/mpc-system/services/service-party-app/electron/main.ts
index affff2fb..3c323cdf 100644
--- a/backend/mpc-system/services/service-party-app/electron/main.ts
+++ b/backend/mpc-system/services/service-party-app/electron/main.ts
@@ -146,13 +146,23 @@ async function checkAndTriggerKeygen(sessionId: string) {
 
     debugLog.info('main', `Session ${sessionId} status: ${status.status} (${status.completed_parties}/${status.total_parties} parties)`);
 
+    // 对于 co_managed_keygen，必须等待所有 N 个参与者加入后才能开始
+    // 这与 server-party 的 waitForAllParticipants 逻辑一致
+    const expectedN = status.total_parties || activeKeygenSession.threshold.n;
+    const currentParticipants = status.participants?.length || 0;
+
+    if (currentParticipants < expectedN) {
+      debugLog.debug('main', `Waiting for all participants: ${currentParticipants}/${expectedN}`);
+      return;
+    }
+
     // 如果会话已经是 in_progress 或 all_joined，或者参与方已满，触发 keygen
     // 使用 status 字段判断是否可以开始
     if (status.status === 'in_progress' ||
         status.status === 'all_joined' ||
         status.status === 'waiting_for_keygen') {
 
-      debugLog.info('main', 'Session ready, triggering keygen...');
+      debugLog.info('main', `All ${expectedN} participants joined, triggering keygen...`);
 
       // 使用后端返回的 participants 信息（包含正确的 party_index）
       // 这解决了 co_managed_keygen 中 server-party 和 service-party-app 混合的问题