回複：不好意思偶比較愚鈍。你是說回國探親是可以的

L2 to H1B is abandoned if you leave US. When out of US in China, no US status needed. Only when you reenter with L2 visa stamp, you regain a new L2 I-94. And the future H1 I-94 comes with the H1 approval is invalid because that COS was based on your old L2-I94.

你是說10月1日前探親回來時要上美領館重新簽證H1B
Yes. Otherwise, you are in US in L2 status, not in H1 status.