A kind of additive which has selfrepairing function for friction pair was prepared with organic molybdenum as the main functional component of self repairing additive and by adding antioxidant and appropriate extreme pressure antiwear agent.Its property were investigated by fourball friction test and gear bench test,and the action mechanism was analyzed with scanning electron microscope and Xray photoelectron spectroscopy.The results indicate that the prepared additive has excellent friction reducing,antiwear and selfrepairing properties.Under mediumlow load,the prepared additive plays a role of friction reducing by forming physical and chemical absorbing film on the surface of friction pair.With the increasing of load and temperature，organic molybdenum and sulfur phosphorus series EPAW components in the prepared additive is decomposed and reacts with the surface of friction pair to form molybdenum disulfide，iron phosphate,ferrous sulfide,molybdenum oxide and other sediments,and these sediments play a role of good lubrication and antiwear effect.Under heavy load,the prepared additive can realize smooth and repair of the wear surface through micro rheological effect.