Abstract: In the present paper, the thermal behavior, viscosity-temperature characteristic, tribological properties and corrosion ability of binary ionic liquid (IL) mixture of 1-butyl-3-methyl imidazolium tetrafluoroborate (L-B104), 1- butyl-3-methyl imidazolium hexafluorophosphate (L-P104) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (L-F104) were investigated by using an STA 449 C Jupiter simultaneous TG-DSC instrumen, a SYP1003-III viscometer, an Optimol SRV-IV oscillating reciprocating friction and wear tester, a MicroXAM 3D noncontact surface mapping profiler and copper strip tests. The results indicate that binary mixture of LB104+ L-F104 was the most suitable IL among the tested samples, L-B104+L-P104, L-B104+L-F104 and L-P104+LF104, to be used as lubricants. The thermal stability of equal molar mixture of L-B104 and L-F104 was similar to that of neat L-F104, and it was increased obviously as compared with neat L-B104. The corrosion level of this binary IL was lower than that of L-B104 and L-F104. The viscosity-temperature characteristic of L-B104+L-F104 was between the characteristic of L-B104 and L-F104. Binary ILs L-B104+L-F104 had good friction-reducing and anti-wear properties both at room temperature and at 100 ℃. Besides good tribological properties, the binary ILs are cost effective in comparison with L-F104.