问题出在 this.addChild( e.target.content );经过测试发现，当loader成功，而不将loader进来的对象� 入显示列表的时候就会报错
所以正确代� �如下
package {
         import flash.display.Loader;
         import flash.display.MovieClip;
         import flash.events.Event;
         import flash.net.URLRequest;

         public class test1 extends MovieClip
         {
                 private var _loader:Loader        
  
                public function test1()                
                {
                    this._loader = new Loader()                
                    this._loader.contentLoaderInfo.addEventListener(Event.COMPLETE,onComplete)
                    this._loader.load( new URLRequest("flexTest.swf"))
                }
  
               private function onComplete(e:Event):void
               {
                  this.addChild( e.target.content );
               }
         }
   }