Friction stir processing (FSP) was summarized in detail. Its effect on properties of materials and the research on preparation of composites and alloys were also introduced. In addition, the problems of FSP research, the prospect and the future development were pointed out. The influencing factors and formation mechanism of the abnormal grain growth need further studies. FSP combined with melt welding can meet the requirement of welding of high strength materials such as titanium alloys. There will be a good application future for FSP to prepare nano-particles enforced metal matrix composites (MMCs) and intermetallic composites (IMCs). An inventive technique to fabricate materials with homogeneous microstructure by adopting the concepts of FSP is pivotal for its applications