This article is concerned with the effects of the silane surface treatment of SiO₂ on the tribological properties of the SiO₂-reinforced poly(methyl methacrylate) (SiO₂/PMMA) composites filled with graphite. Silane treatment and graphite bring positive effect on the improvement of friction reducing and antiwear of SiO₂/PMMA composites. Fourier transform infrared spectroscopy analysis shows that the SiO₂ has been oxidized and etched by the silane treatment. The presence of active groups increases the polarity of SiO₂, and hence the bond property between the particle and matrix is improved.