Abstract: Influence of SiO2 content on the properties of Cu-SiO2 composites, fabricated by powder metallurgy method, was studied. Its tribological properties related to the sliding speed, SiO2 content, and third bodies were investigated by a pin-on-disk tester with speed ranging from 7.8 to 47 m/s. Friction coefficient, hardness and porosity increased while the wear rate and the volume density decreased with increasing SiO2 content. The third body configuration strongly depended on the sliding speed. At lower speeds, the third bodies were porous and were readily detached from the substrate, resulting in larger wear. At higher speeds, the third bodies were dense and sticked to the surface strongly due to higher temperature, which decreased the wear while it increased the friction coefficient. However, too high temperature may weaken the substrate which supporting the hard SiO2 particles, and as a result, the wear increased. On the other hand, at high temperature, the plasticity of the third bodies was relatively good and led to decreased friction coefficient.