For Indian passport holders and Saudi Arabia passport holders, the requirements for a business visa are as follows (doesn't make much difference):
A: A letter of invitation from China

(a)Applicants holding invitations from company in China may apply for single or double entry visas.

(b)Applicants holding an original notice of visa authorization from a duly authorized Chinese organization in China, namely, Ministries and Commissions of the State Council, the Government of all Provinces, Autonomous Regions, and Municipalities directly under the Central Government, and Foreign Affairs Offices and Bureaus of Economy and Commerce thereunder, and departments and units recognized by the Department of Consular Affairs of the Ministry of Foreign Affairs of the People’s Republic of China, with a multiple entry visa notification may apply for multiple entry visas.

B: Covering letter from applicant's company or employer addressed to the visa office.