The preparation of a series of dispersible nano-SiO 2 by surface-modification in situ was described in this paper. It is found that some silane coupling agents can be combined with nano-SiO 2 by covalent bonds, which change the nanoparticle's surface properties and make nano-SiO 2 disperse well and steadily in many organic mediums. The structure of nanoparticles was characterized by transmission electron microscopy (TEM), infrared spectrum (IR), X-ray photoelectron spectra (XPS) and thermogravimetric analysis (TG). The dispersivity of these nanoparticles in organic solvents was measured by light transmittance. Considering such superior dispersion in oily solvents and very small size, we primarily investigated their tribological behaviors as additive in lubricant on wear testers. The results show that they can evidently increase anti-wear ability and reduce the friction coefficient of lubricant.