Abstract: The tribological properties of some ionic liquids were investigated as additives in polyethylene glycol. Scanning electron microscope (SEM) and X-ray photoelectron spectroscope (XPS) analyses were conducted to examine the morphology and chemical composition of the wear scars. The results showed that the ionic liquids presented excellent friction-reducing and antiwear properties. This is probably because that the ionic liquids adsorbed on the frictional surfaces and formed protective tribolayers during test.