The acid modification of multimall carbon nanotubes (MWNTs) was performed by an HNO3/H2SO4 solution. The glycidyl methacrylate (GMA) undergoing all opening-ring was grafted onto the surface of acid-modified MWNTs. The surface properties of MWNTs were investigated by Fourier transform infrared spectrometer (FTIR), Raman spectra, transmission electron microscopy (TEM), X-ray diffraction, and thermogravimeric analysis. Then the MWNTs/poly(methyl methacrylate) (PMMA) nanocomposites were prepared by in situ polymerization. The tribological and dielectric properties of nanocomposites were Studied. As a result, GMA was grafted on the Surface of MWNTs. The tribological and dielectric properties of MWNTs/PMMA nanocomposites were improved as the content of the surface-modified MWNT increased. The marked improvement in tribological and dielectric properties were attributed to the good dispersion of MWNTs that were bonded with C=C on the surface that participated in the polymerization of MMA. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 1755-1761, 2009