回复：多谢，我还以为只要绿卡就可以了呢。

if entry from Canada or Mexico, GC without passport is fine. If entry from China, you need a passport, or a travel document showing you have no nationality. but 只要绿卡就可以了 is also true, if you plan do stay in the airport immigration station for the whole day to let them inspect you all over for hours and hours.