Two kinds of lubricating additives were synthesized via the reaction of acidic phosphate and acidic thiophosphate with epoxidized soybean oils respectively.The friction reducing and antiwear properties of the additives in ester oil were investigated by SRV friction machine.The maximum non seizure load values of the lubricant were carried out using four ball machine.The results show that the additives with mass fraction of 1% in ester can dramatically reduce the friction coefficient and wear volume,and the minimum wear volume is only the 1/10 of that of the base fluid lubrication.The morphology and chemical composition of the rubbing surface were analyzed by scanning electron microscope and Xray photoelectron spectroscopy.The result shows that the excellent friction reducing and antiwear properties of the lubricant additive can be attributed to the formation of iron oxides,iron sulfide,and iron phosphate during the rubbing process.