Isobaric vapor liquid equilibria (VLE) data of the ternary system methanol + ethanenitrile +1-ethyl-3-m ethylimidazolium bis(trifluoromethylsulfonyl) imide ([EMIM] [NTf2]) and methanol + ethanenitrile +1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([BMIM][NTf2]) as well as their binary system methanol + ethanenitrile (MeCN) were obtained using a improved Othmer still at 101.3 kPa. Results indicated that the addition of [EMIM] [NTf2] or [BMIM] [NTf2] can eliminate the azeotropic phenomenon of the binary system of methanol + MeCN when the mole fraction of the ionic liquids reach 0.05. Besides, the measured ternary data were well fitted with the nonrandom two-liquid model.