The graphite nanoparticles prepared in water were introduced to lubricating oil by phase transfer. Tribological experiments were performed to determined anti-wear capability, load capacity and friction coefficient of the modified lubricant. The graphite addition reduced the diameter of friction scar from 0. 52 to 0.46 mm and the friction coefficient from 0. 086 7 to 0. 061 2 while having no effect on the load capacity. The graphite layers formed by the nanoparticles prevented the immediate contact between the two sliding sides. The test results demonstrated improved tribological properties of the graphite nanoparticles modified lubricant.