The tribological behavior of TiN nanoparticle as lubricating additive was studied in MRS10 fourball frictional apparatus.The frictional wear behavior and selfrepair characteristic was analyzed by using Grinding Spot measurement system,Laser Scanning Confocal Microscope OLS1100 and EDS measurement instruments.Experimental results indicate that TiN nanoparticles possess good friction reducing and antiwear characteristics.The best friction reducing and antiwear effect of the lubricating oil is reached by adding 05% nanoparticle additive and 10% PEG200 dispersing agent.The lubricating oil with TiN nanoparticles has better selfrepair and surface polishing effect at high loads.