Has anyone filed immigration visa for you before?
If asnwer yes, is there any problem to get visa stamp in china?
A: Filing I-485 should not be a reason to deny your H1B visa, since H1B allows dual intention(immigration intention). I wouldn't worry too much about this. I would ask around to see if security check can cause any delay in getting the visa. (I know F1 visa case being delayed by security check, but don't case about H1B visa)