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如果我理解的对， 是说如果我先生六月入境美国，他必须在七月十七号离境。除非，他在我收到H1B后，在美境内申请H4延期。

不知再美境内申请延期要多长时间。

-Your spouse can apply for the H-4 status extension (file I-539) immediately after he enters US using the H-4 visa even if your H-1 extension is pending. He just needs to provide the copy of your current H-1 approval notice with I-94,  the copy of your H-1 extension Receipt Notice, the copy of your marriage certificate (may also the paycheck stubs of your latest three months). 

His H-4 extension application only can be approved after your H-1 extension is approved and his new H-4 status duration is the same as your new H-1 status duration.

谢谢帮助！