A concentration-dependent surface area parameter model (Iwai, Fluid Phase Equilibria, 465 (2018) 24–32) was modified to avoid the restriction conditions for the parameters of the pure components. The model is applied to correlate the ternary liquid-liquid equilibria and constituent binary phase equilibria with one set of binary parameters. The correlated results for both vapor-liquid equilibria and liquid-liquid equilibria obtained by the model are better than those of the NRTL and UNIQUAC models. The model simultaneously represents the experimental data at multiple temperatures of liquid-liquid and vapor-liquid equilibria with one set of parameters.