The solid-liquid phase equilibrium for ternary system of 4-chlorophthalic anhydride + 3-chlorophthalic anhydride + acetone was measured at different temperatures and the mutual solubility was obtained. Four isothermal phase diagrams were constructed according to the experimental solubility. There existed two pure solid phases at each temperature in the studied system, pure 4-chlorophthalic anhydride and pure 3-chlorophthalic anhydride, which were identified by the wet residue method of Schreinemakers'. The crystallization regions of the pure two solids increase with the decrease in temperature. The experimental solid-liquid phase equilibrium for ternary system was calculated using the Wilson and NRTL models, and the corresponding binary interaction parameters were obtained according to the solubility of binary system. The calculated results agree well with the experimental data at different temperature. Both the models give acceptable results for the investigated systems. (C) 2013 Elsevier B.V. All rights reserved.