Abstract:New nanomaterials of graphene as themineral oil’s lubricant additives have been studied extensively,but very few researches are related to the vegetable oil.With the castor oil as the base oil,the graphene modified with oleic acid as the additive,the mixed castor oils with different weight content of modified grapheme were prepared,and the lubrication properties were investigated by using fourball friction testing rig.The results show that the modified graphene can improve the lubrication performance of castor oil,when the weight content of modified grapheme reaches 0002% in the mixed castor oil,the wear scar diameter and the average friction coefficient are decreased by about 148% and 237%,respectively,and the degree of the worn surface of the steel balls is the lowest.Furthermore,the results indicate the synergy between modified graphene and castor oil is not significant at initial stage of the test,but improving the lubricating performance of castor oil at the late stage.