any sponsorship or invitation letter required from China government?

Sunil, you need the following documents: your passport, a photocopy of the passport’s data page, a filled-out application form affixed with your recently-taken color bare-headed photo, and an invitation letter from your trade partner. It’s likely that you may also need to submit an invitation letter from the Duly Authorized Unit, a local company cover letter, a copy of the company’s bank statement, and a copy of its business registration certificate. The Duly Authorized Unit invitation letter is issued by a provincial foreign affairs office or the chamber of commerce in China. You should obtain it with the help of your trade partner.