Document necessary for Spouse

Hi,

I'm a citizen of Bangladesh. Now I've been in China for last 6months in H&M. My contract is for 1 year in total. now I would like to bring my wife here at Shanghai and she will stay for 6months till to the end of my contract. So what kind of visa she needs to apply for and what are the necessary document my wife needs to prepare for application.
Does she need any invitation letter from my company or China govt.
FYI, my company has applied for the invitation letter but govt refused to provide any invitation letter for her.