Liquid-liquid equilibrium data of the quaternary system of water + acetic acid + methyl tert-butyl ether (MTBE) + NaCl at 298.15 K have been measured under atmospheric pressure. The liquid-phase splitting of the water + acetic acid + MTBE can be enhanced by the addition of salt NaCl. Selectivity of MTBE at different NaCl concentrations was calculated and compared. In addition, the experimental data were correlated with the NRTL and electrolyte-NRTL model. Also, parameters of these two models were regressed.