I want stamp my visa from India to China. I have a invitation letter from china Quilting factory.

If you are working and living in Saudi Arabia, you may just apply for your China visa from the embassy or consualte of China there. Of course, if you are Indian passport holders, you may also apply for the visa in your home country. Besides the invitation letter from the China factory, you may also ask them to provide a confirmation of invitation by their local authorized Chinese government unit such as the foreign affairs office.