Abstract: Three kinds of phosphonate ionic liquids were synthesized and used as lubricants for steel/tin bronze contact. The tribological performance of the lubricants was evaluated on an optimal SRV-IV oscillating friction and wear tester. The worn surfaces of the tin bronze were analyzed by a JSM-5600LV scanning electron microscope and a PHI-5702 multifunctional X-ray photoelectron spectrometer. Results show that phosphonate ionic liquids performed better lubricating properties than conventional ionic liquid lubricant 1-butyl-3-methylimidazolium hexafluorophosphate and the perfluoropolyether under room and high temperatures. The excellent lubricating properties of the phosphonate ionic liquids were attributed to the formation of adsorption films and the tribochemical reaction films attaching to the metal surfaces.