diff --git a/packages/designer/src/project/project.ts b/packages/designer/src/project/project.ts
index 082554846..b5a553627 100644
--- a/packages/designer/src/project/project.ts
+++ b/packages/designer/src/project/project.ts
@@ -369,6 +369,10 @@ export class Project implements IProject {
   }
 
   onSimulatorReady(fn: (args: any) => void): () => void {
+    if (this._simulator) {
+      fn(this._simulator);
+      return () => {};
+    }
     this.emitter.on('lowcode_engine_simulator_ready', fn);
     return () => {
       this.emitter.removeListener('lowcode_engine_simulator_ready', fn);
diff --git a/packages/shell/src/api/project.ts b/packages/shell/src/api/project.ts
index 04feb81f3..a409cbcd5 100644
--- a/packages/shell/src/api/project.ts
+++ b/packages/shell/src/api/project.ts
@@ -192,12 +192,8 @@ export class Project implements IPublicApiProject {
    */
   onSimulatorHostReady(fn: (host: IPublicApiSimulatorHost) => void): IPublicTypeDisposable {
     const offFn = this[projectSymbol].onSimulatorReady((simulator: BuiltinSimulatorHost) => {
-      this[simulatorHostSymbol] = simulator;
       fn(SimulatorHost.create(simulator)!);
     });
-    if (this[simulatorHostSymbol]) {
-      fn(SimulatorHost.create(this[simulatorHostSymbol])!);
-    }
     return offFn;
   }