Abstract: Three kinds of room temperature ionic liquid (C_nmimhfac, n=4,6,8) lubricants containing hexafluoroacetylacetone anion and imidazole cations were synthesized. Taking 1-butyl-3-methylimidazolium bis(trifluoromethyl)sulfonylimide (L-F104) as a control sample, the lubricating and physicochemical properties of the ionic liquid as lubricants for different friction pairs were studied, and the influence of the length of cationic alkyl chain on their properties was explored. The results show that the ionic liquids were less corrosive to the metal substrates. At room temperature, they had good lubrication performance on steel/copper and steel/aluminium friction pairs. With the increase of cationic alkyl chains, their thermal stability and viscosity increased, and their friction reducing and anti-wear properties were also improved.