Abstract: A new type of envionmentally friendly lube additive- sulphurized rapeseed oil lube additive was prepared and the chemical structure was characterized by infrared spectrum. Tribological properties of the additive in rapeseed base oil were evaluated on friction testers. Tribochemical species of the worn surfaces were analyzed by means of X-ray Photoelectron Spectroscope(XPS).Results show that the additive is excellent in increasing load carrying capacity, antiwear and friction-reducing abilities of rapeseed oil. It is inferred that a high strength adsorption film and a tribochemical reaction film formed on the rubbing surfaces due to carrier effects of long chain rapeseed oil molecules, high reaction activies of sulfur and their synergisms.