The phosphate ionic liquid,which has low corrosion and is simple and easy to be synthesized,was used as base oil,the PTFE powder was used as thickening agent,a new kind of ionic liquid lubricating grease was prepared.The tribological properties of phosphate ionic liquid lubricating grease for steel/steel pairs were studied on Optimol SRV tester.The results show that the phosphate ionic liquid lubricating grease shows better friction reducing and antiwear properties at room temperature and high temperature(100 ℃).The friction reducing and antiwear properties are closely related with the cation and anion alkyl chain length of the ionic liquid.The results of SEM and XPS analysis show that there exists the chemical reaction film containing FeF2 and FePO4 and nitrogen oxide which is formed by the friction chemical reaction between the ionic liquid lubricating grease and the friction surface,and the adsorption film containing PTFE on the friction surface.