In this article, the surface Of SiO2 nanoparticles was modified by silane coupling agent N-(2-aminoethyl)-gamma-aminopropylmethyl dimethoxy silane. The bismaleimide nanocomposites with surface-modified SiO2 nanoparticles or unmodified SiO2 nanoparticles were prepared by the same casting method. The tribological performance of the nanocomposites was studied on an M-200 friction and wear tester. The results indicated that the addition of SiO2 nanoparticles could decrease the frictional coefficient and the wear rate of the composites. The nanocomposites with surface-modified SiO2 nanoparticles showed better wear resistance and lower frictional coefficient than that with the unmodified nanoparticles SiO2 The specific wear rate and the steady frictional coefficient of the composite with 1.0 wt % surface-modified SiO2 nanoparticles are only 1.8 x 10(-6) mm(3)/N m and 0.21, respectively. The dispersion of surface-modified SiO2 nanoparticles in resin matrix was observed with transmission electron microscope, and the worn surfaces of pure resin matrix and the nanocomposites were observed with scanning electron microscope. The different tribological behavior of the resin matrix and the filled composites should be dependent on their different mechanical properties and wear mechanism. (C) 2008 Wiley Periodicals, Inc.