Abstract: A series of SiO2 nano-particles were modified by different solvents and modifiers and characterized by SEM technique. The dispersing properties and tribology performance of the modified particles were investigated to screen out the best solution and modifier. The tribology performance of the lubricant adding the best modified SiO2 was tested to determine the optimal amount of modified SiO2 nano- particles. It is found that ethanol is the suitable solvent for SiO2 naoparticle surface modification, and the best modifier is KH-550. The best way to use KH-550 is to prepare KH-550 alcohol solution first and then add into the lubricant system. The lubricant with 2% (w) modified SiO2 nano-particles has the best anti-wear and anti-friction performance.