A useful model has been proposed to calculate liquid-liquid equilibria (LLE) of non-aqueous ternary systems, which are classified as type I (only one pair among binary systems is partially miscible), based on a modified Wilson equation. The modified Wilson equation adopted contains the interaction energy parameters of constituent binary systems and the multi-component parameter for the ternary system concerned. In this study, a simple procedure has been developed to estimate those parameters from normal boiling points and solubility parameters which can be obtained by a group-contribution method. Therefore, LLE of ternary systems can be calculated by using pure-component properties alone. The procedure has been adopted for various alkane+methanol+aromatics ternary systems and good correlation performances are obtained.