Abstract: Low temperature ion sulfuration was used to treat 52100 steel in order to improve its wear -resistance and anti- scuffing property . Two different sulfur -containing extreme pressure and anti wear additives were used to examine their synergistic effects with FeS layer . The tribological properties were investigated on a ball- on- disk sliding friction and wear tester . SEM was employed to analyze the morphologies of worn surface , and XPS was adopted to identify the valence state of typical elements of boundary lubricating film and detect the depth Profile of elements . The results showed that sulfide layer on the surface prevented the additive and the substrate from direct contact and inhibited the effect of additive . The solid - liquid composite lubrication Possessed an obvious synergistic effect when the duration of FeS layer was long . The sulfllr -containing additives reacted with substrate to form FeS to supplement the loss of sulfide layer in wearing process . This incarnated the beneficial synergistic effect of composite lubrication . Sulfuration olefin (SO ) with high activity had better replenishinge effect than that of zinc dialkyl dithiophosphate ( ZDDP ) whose activity depended on catalysis of temperature.