Isobaric vapor-liquid equilibrium data for {methanol (1) + dimethyl carbonate (2) + 1-octyl-3-methylimidazolium (3)} where 3 is an ionic liquid ([OMIM](+)[BF4](-)) were obtained at 101.32 kPa using a modified Othmer still. The results indicated that [OMIM](+)[BF4](-) can transfer the azeotropic point and totally eliminate the azeotropic phenomena when its mole fraction is up to x(3) = 0.20. This shows that [OMIM](+)[BF4](-) could be used as a alternative entrainer in the extractive distillation for methanol (1) + dimethyl carbonate (2) system. The measured ternary vapor-liquid equilibrium data were fitted with the NRTL.