Abstract: Semimetallic friction materials are a new kind of engineering materials which deserveto be developed.They have many advantages,such as stable friction coefficient,excellent wear-resistance,little environmental pollution and little damage to counterpart. But,the action offriction heat,interface stress and some other factors make elastic deformation,element diffusionand ingredient transfer take place in worn surface layers.Thereforce,the characteristics of wornsurface layers of the sliding friction pair consisting of the semimetailic friction material reinforcedwith brass fibers and grey cast iron were investigated , and the influences of worn surface layers onfriction-wear behavior were analyzed by scanning electron microscope(SEM),energy dispersiveanalysis of X-ray(EDX) and differential thermal analysis-thermogravimetric analysis( DTA-TGA). The results showed that under the given experimental conditions,the surface layer with richiron and poor copper was formed in the surface worn region of the semimetallic friction material,the depth of organic ingredient pyrolysis caused by friction heat in worn surfaces was atout 0.35mm; the semimetallic friction material containing 15%-20%of Cu had better wear-resistance,and can form a even and continuous transfer film of copper; crack peeling was the importantmechanism of the counterpart.The experimental results also provided a scientific basis for the studyand application of semimnetallic friciton materials.