Abstract: Using quaternary ammonium salt and lauric acid sodium salt as process control agents, surface modificated Nano TiO₂ powders were prepared in situ by plasma assisted ball milling, and the tribological properties of the powders were studied. Due to synergistic effect of plasma hot explosion and pulse electron bombardment, the mean size of prepared powder was refined to 20 nm and the crystalline structure was transformed from anatase to rutile after plasma assisted ball milling for 11 h. Surface modificated Nano TiO₂ powders were well dispersed in 40CA marine lubricant owing to its oleophobicity characteristics. Lubricant with Nano TiO₂ additive showed lower friction coefficient and better wear resistance than that of base oil because of the micro-bearing effect of the TiO₂ nanoparticles. Scratches on worn surface can be repaired by adsorption and deposition of Nano TiO₂ powders. Therefore compounded lubricant exhibited favorable anti-friction quality and self-repairing performance.