回复：请教, H4从中国回美,是否要在中国申请签证? 谢

Canadian citizens no need a visa to enter US. you do need you H-4 status doc (I-797 etc.) to get the H-4 category on you I-94 and passport. otherwise you may still enter US but will be a B2-like category which may cause some problem later if you stay too long.
airline may not ask canadians for I-94 when leave US but give it out is better although not so strict.