Do you hold a residence permit of Mainaland China now? if not, please don't leave Mainland China, once you exit Mainland China, you have to apply for a new work visa to return to Mainalnd China. Z visa holders should obtain the residence permit within 30 days after entry. Z visa is generally valid for 3 month and no duration of stay. Applicants should apply for a residence permit from a local county level Public Security Bureau within 30 days after entering China.