The friction and wear prosperity of diesel soot and nanographite as lubricant additives in PAO4 oil was investigated by using ballplate reciprocating mode on the UTM-2 machine at different temperatures (25,100,175 ℃).The antifriction characteristics and lubrication mechanismwere analyzed by means of light microscopy,scanning electron microscopy,threedimensional morphology,and Raman spectroscopy.The result of AFM analysis displays that the particle size of diesel soot is between 20 nm and 70 nm,the nanographite,with particle size between 10 nm and 30 nm,is slightly smaller in particle size than the diesel soot.Diesel soot and nanographite of 0.01% in the lubricant play well antwear effect,which can reduce the friction coefficient by 50% to 80%,reduce the wear rate by 40% to 70%.The antiwear mechanism is that a protective film is formed on the worn surfaces by diesel soot and nanographite,which changes the frictional contact interface environment.