In order to study the effect of different extraction methods on the extraction of base oil from lithium grease,lithium grease was prepared by thickening base oil with 12-hydroxy stearic acid system,and two different methods,the method of petroleum ether extraction and the method of pressure oil separation,were used to extract the base oil from the asprepared lithium grease.The differences of viscosity,group composition,low temperature performance and component structure between the base oils extracted by two different methods and the original thickened base oil were analyzed.The results show that the infrared spectrum of the base oil extracted by two different methods is basically the same as that of the original thickened base oil,and the group composition and aniline point are also basically the same as that of the original thickened base oil.The viscosity,viscosity index,pour point and evaporation loss of the base oil extracted by the method of pressure oil separation are in accord with original blended base oil.The viscosity of the base oil extracted by the method of petroleum ether extraction is basically the same as that of the small viscosity base oil in the blended base oil,the viscosity index and pour point are related to the consistency of the grease,and the evaporation loss is slightly greater than that of the original thickened base oil.For the analysis of lubricating grease composition,two methods can be used together to get more accurate results.