回复：老公H1B我H4,多次往返，仍在有效期内。已去过一次美国，现在国内。现H4可否单独进入美国？

All depending on H1's employment, if he is still employed by the H1 sponsor, your H4 is good even if he is currently not in US. If already terminated, your H4 is invalid even if your visa stamp is still good.