For separation of the azeotrope isobutyl acetate and isobutyl alcohol, imidazolium-based ionic liquids 1-hexyl-3-methylimidazolium hexafluorophosphate [Hmim] [PF6] and 1-octyl-3-methylimidazolium hexafluorophosphate [Omim][PF6] were applied as the extractants in the extraction process. The liquid liquid equilibrium (LLE) data for the ternary systems isobutyl acetate + isobutyl alcohol + [Hmim][PF6]/[Omim][PF6]) were determined at temperature of 298.15 and 308.15 K. To evaluate extraction performance of the ILs, the selectivity and distribution coefficient were calculated from the experimental data. The effect of the alkyl chain length of the cations and the temperature on the LLE for the systems were explored. In addition, the experimental LLE data were correlated by the NRTL model, and the binary interaction parameters of the NRTL model were optimized.