Glass fiber (GF)/epoxy (EP) composites added by carbon nanotubes (CNTs) were fabricated to investigate the effects of CNTs on the friction and wear properties of GF/EP composites. The surface of the CNTs was treated with acid mixtures to improve their dispersion in the GF/EP composites. The changes of surface properties of CNTs were investigated by using fourier transform infrared spectroscopy. Ring-on-block type wear tests were performed to evaluate the frictional properties of composites. Results show that CNTs after acid treatments can improve the wear resistance and reduce the friction coefficient of GF/EP composites more remarkably than CNTs. The surface fracture of the composite was observed by scanning electron microscope.