A modified Othmer still was used to measure the vapor-liquid equilibrium data for the ternary system chloroform + methanol + 1,3-dimethylimidazolium dimethylphosphate ([MMIM](+)[DMP](-)) at 101.3 kPa. The measured data were correlated with the NRTL model proposed by Renon and Prausnitz (1968), with the mean absolute deviations between calculated and measured gas-mole fractions of chloroform equaling to 0.004. The results showed that [MMIM](+)[DMP](-) brought about an obvious salting-out effect, and the NRTL model predicted that the azeotropy would be eliminated with the mole fraction of [MMIM](+)[DMP](-) up to 0.028 at 101.3 kPa.