This work tries to explore the relation between molecular structures of ionic liquids (ILs) as entrainers and separation performance on ethyl acetate (1) and ethanol (2). The vapor-liquid equilibrium (VLE) data have been measured for ethyl acetate (1) + ethanol (2) containing ILs at 101.32 kPa. The ionic liquids investigated were 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM](+)[BF4](-)) and 1-methyl-3-octylimidazolium tetrafluoroborate ([OMIM](+)[BF4](-)), as well as 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM](+)[Br-4](-)) that has been studied in our previous work, All the ILs could give rise to the salting-out effect. It was found that, at low IL concentration, the separation ability of ILs is in the order [EMIM](+)[BF4](-) > [BMIM](+)[BF4](-) > [OMIM](+)[BF4](-), while at high IL concentration (x(3) = 0.10-0.30) the separation ability of ILs is in the order [OMIM](+)[BF4](-) > [EMIM](+)[BF4](-) > [BMIM](+)[BF4](-) due to the difference of polarity of the three ILs and demixing effect. [EMIM](+)[triflate](-) was included as entrainer and compared with the tetrafluoroborate-based ILs. The measured ternary data were correlated using the NRTL model.