In order to improve the anti-wear performance of edible soybean oil(SO) as lubricant,a modified soybean oil(MSO) was synthesized in a mild reaction environment by using enzyme Novozym435 as catalyst to carry out the epoxidation of unsaturated fatty acids in SO with methanol.The structure was characterized by infrared and Raman spectrometers,the thermal oxidation stability was investigated by synchronous thermal analyzer TG-DSC,and the friction and wear performance of MSO was investigated on a four-ball machine.The scanning electron microscope,three-dimensional surface profilometer,and Raman spectroscopy were used to analyze the micro-morphology and composition changes of the frictional spot surface.The results show that the acid value and iodine value of modified soybean oil decrease significantly,the saturated fatty acid content increases,and the thermal oxidation stability is enhanced.The anti-wear performance of MSO is significantly improved,the spot diameter decreases by 25.56%,and the wear volume decreases by 54.18%.The excellent wear resistance of MSO is mainly related to the content of saturated fatty acid,the excellent thermal oxidation stability and the ordered lubrication film formed on the wear surface.Due to the improvement of its thermal oxidation performance,the action time of the formed orderly lubrication film in the lubrication process is greatly increased,so as to more effectively resist the wear in the friction process.