I want to join a teaching job in china

And can i get double entry visa?

To apply for a work Z type from the Chinese embassy in your country, you should first prepare those documents including your passport and copy of its data page, a completed application form, recently-taken passport-style photo, and a work permit from your employer. Just for your reference. After you get the work Z, you can enter China to get a residence permit. The residence permit has multiple entries.