Pls i have an invitation letter now so my question is do i need any other thing to back it up?

You need to provice following documents for business visit:
Qualified original introduction letter with the full name, title, date & signature of the issuing person from your company; the original and one photocopy of your ID card, the original and one photocopy of the certificate of incorporation of your company, hotel reservation in China and round-trip ticket; recent bank statement of account; one photocopy of passport pages with Chinese visa if any and any proof of business connection with the inviting company in China (e.g. fax of business negotiation, contract, agreement, quotations of goods, invoices, bill of lading.)