What is the process needed in order to get one year or six months multiple visa to china?

First, if all of you haven't been to China before, then I am afraid that your chance of applying for the multiple ones is very low. The procedure is the same as that for single-entry M type. You prepare all required documents, passport, application form, passport photos, invitation letter from that Chinese company, invitation letter from duly authorized Chinese unit and your valid resident permits in Saudi Arabia. Then you submit all the documents to Chinese embassy and wait for approval. It usually takes around four working days.

However, I personally think that you should find an agency to help you. The agencies are much more capable.