A kind of novel compound containing S and Mo elements was synthesized. Its chemical structure was characterized by elemental analysis, IR and NMR. Its anti-wear property and the load-carrying capacity, as an extreme pressure (EP) additive of lubricating oil, were investigated using a four-ball tester. The experimental results show that the additive exhibits a superior anti-wear property and a high load-carrying capacity .The presence of other additives does not interfere with the anti-wear property of the extreme pressure additive. The influences of load and temperature on the property of the additive were examined. The possible mechanism was investigated by means of surface analysis of the tested steel ball specimen, using XPS. The lubrication films formed on the rubbing surface are mainly composed of MoS_2,MoO_3 and MoO_2. Its chemical structure was characterized by elemental analysis, IR and NMR. Its anti-wear property and the load-carrying capacity, as an extreme pressure (EP) additive of lubricating oil, were investigated using a four-ball tester. The experimental results show that the additive exhibits a superior anti-wear property and a high load-carrying capacity. The presence of other additives does not interfere with the anti-wear property of the extreme pressure additive The influences of load and temperature on the property of the additive were examined. The possible mechanism was investigated by means of surface analysis of the tested steel ball specimen, using XPS. The lubrication films formed on the rubbing surface are mainly composed of MoS_2, MoO_3 and MoO_2.