Vapor liquid equilibiria (VLE) were measured for systems containing 1-methyl-3-ethylimidazolium diethylphosphate ([EMIM] [DEP]) ionic liquid (IL) in the temperature range from 310 K to 390 K. The systems include 1-propanol + [EMIM][DEP], 2-propanol + [EMIM][DEP], water +1-propanol + [EMIM][DEP], and water + 2-propanol + [EMIM][DEP]. [EMIM][DEP] was divided into one 1,3-dimethylimidazolium dimethylphosphate ([MMIM][DMP]) and three methylene (CH2) electrically neutral groups. And then the experimental VLE data for binary systems containing [EMIM][DEP] were regressed using the modified UNIFAC model with the maximum average relative deviation (ARD) of 2.7 %. The newly obtained interaction parameters between groups allowed the reliable prediction of other binary and ternary systems containing [MMIM][DMP] and [EMIM][DEP] without parametrization. It was found that both of the ILs can give rise to the salting-out effect, and lead to a breaking of the azeotropic behavior of alcohols + water mixtures. [MMIM][DMP] shows a higher separation ability for the azeotropic mixture studied than [EMIM][DEP].