what documents are required for China business visa for Srilankan passenger

You will go there for business meetings or for pruchasing something?
If go for purchasing, you need to prepare for an Invitation Letter of Duly Authorized Unit, an invitation letter from your Chinese partner, your own company's introduction letter, bank statement (at least containing 3 months' history), your company's Business Registration Certificate.

If you go there for meeting or exchanging, you need to provide same documents, but just do not need to show the Business Registration Certificate.