In this research, solid-liquid equilibrium for the ternary system (2-naphthaldehyde + o-phthalic anhydride + 1,4-dioxane) was measured at 283.15 K, 293.15 K and 303.15 K, respectively. Three isothermal phase diagrams of the system were plotted using the values of the experimental solubility. Pure 2-naphthaldehyde and o-phthalic anhydride were formed at (283.15, 293.15 and 303.15) K, and were determined by Schreinemaker's wet residue method. The crystallization region of o-phthalic anhydride was found to be much larger than that of 2-naphthaldehyde at a certain temperature. The experimental solubility at multiple temperatures was correlated by the NRTL and Wilson models. The NRTL model was more accurate than the Wilson model in this system. The diagram of density versus component was also constructed. (C) 2016 Elsevier Ltd.