A series of synthetic ester based ionic liquids were prepared by using pentaerythritol ester (5750) and the Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) via “in situ” synthesis method,and their themal stability,evaporation loss,tribological performance as well as antioxidation properties were studied.Experimental results demonstrate that the developed lubricants exhibit outstanding thermal and oxidation stability compared with the 5750.When the ratio of Li and 5750 is 15∶1,the initial decomposition temperature of the synthetic ester based ionic liquid is increased by 33 ℃,50% decomposition temperature is increased by 99.4 ℃,and evaporation loss is decreased by 619% in 192 hours.Synthetic ester based ionic liquid with the ratio of Li and 5750 at 1∶1 posses the best tribological properties,which can reduce the friction coefficient and wear scar diameter by 32% and 56%,respectively,compared with the 5750.Synthetic ester based ionic liquid shows good receptivity with amine antioxidant.