Hey Carl,
First,thanks for replying me.
I know as3 is going to die,but my company still have some products need to maintain so...
Anyway, I have done lots of tests.
I think it's not the SWFLoaderVars's problem,even I use the AS3 Loader got the same problem too.
so i use FlashBuilder's "Flash Profile", i found the external class I have loaded was located at a method called "[execute-queued]" here's some detail about it https://forums.adobe.com/thread/432052?tstart=0
I think it can not be control.
so I change it like this, and i'm glad it works.
it's the best solution i think..
var context:LoaderContext = new LoaderContext(false, new ApplicationDomain(ApplicationDomain.currentDomain), SecurityDomain.currentDomain);
var vars:Object = {name:"test", context:context, onComplete:onComplete};
var swfLoader:SWFLoader = new SWFLoader("resource/test.swf", vars);
swfLoader.load(true);
thanks again.