感謝各路英豪傑的幫忙,

I summarized what you said
(1)Because my H1-B was approved,if I enter Canada and can get a new I-94 card,then I can legally come back to USA even if I have no AP
(2)If I enter Canada and fail to get a new I-94 card,I may be rejected when I enter USA and my I-485 will be invalidated.

That means that It is better for me to apply for an AP even if there is no or less risky to get a new I-94 in Canada.

Thanks a lot