In this paper, a 20nm inorganic mineral particles, mainly includes Mg3Si2O5(OH)4, KAlSiO4 and CaMg(CO3)2, were prepared by the ultrasonic nanometer grinder. As a lubricating oil additive, the dispersion property of the particles was characterized and the tribological properties were evaluated. The antiwear mechanism was investigated with SEM, EDS and XRD. Results show the inorganic nano-mineral material as an oil additive has excellent stable-dispersion property. The load-carrying capacity and antiwear property of the base oil were improved greatly. It can be inferred that the additive creates certain deposit on the friction surface. The physical-chemical deposition could not only bear the load but also prevent forming direct contact of two rubbing surface. 0.5wt% is the optimal additive concentration.