Quaternary vapor−liquid equilibrium (VLE) data were measured for the system of ethanol/water/ethanediol/potassium acetate (KAc). Binary salt-containing VLE data were correlated with the salt-containing local composition model (SCLCM). For a multicomponent system, ternary and quaternary VLE data predicted by SCLCM are in agreement with the literature data and data in this work. The influence of KAc, ethanediol, and the mixture of KAc and ethanediol on the system was investigated by the SCLCM method, and the results showed that the additives have different influences on the volatility of ethanol and water. The calculation method of the salt-containing VLE is simple and effective for the system.