Friction stir processing (FSP) is a new type of plastic deformation processing method and proposed on the basis of Friction Stir Welding (FSW). Since it was invented, researchers have succeeded in applying FSP to refine microstructure of casting metal, prepare superplastic material, modify surface characteristic of materials, and prepare composite materials. The processes of friction stir processing and friction stir welding are basically the same and the process parameters on the friction stir processing has a great impact on material quality. The summarized research progress of friction stir processing in recent years mainly includes two categories: FSP without reinforcing phase and FSP with reinforcing phase. FSP without reinforcing phase mainly consists of casting microstructure refinement and superplastic material preparation. FSP with reinforce phase mainly includes surface modification of materials and preparation of composite materials. Friction stir processing of composite materials is divided into non-situ synthesis of composite materials and in-situ synthesis of composite materials according to whether the added phase reacts with the substrate to produce enhanced phase,. The paper summarizes and comments on the above contents respectively, and finally points out the direction of future development and application of FSP.