The study of the solid-liquid phase equilibrium for the [HAE]Cl-MgCl2-H2O system is of significance for the preparation of anhydrous magnesium chloride using the thermal decomposition of the complex ([HAE]Cl center dot MgCl2 center dot 6H(2)O), which is synthesized by the reaction of aniline hydrochloride ([HAE]Cl) and bischofite (MgCl2 center dot 6H(2)O). In this study, a rigorous and thermodynamically consistent representation for the [HAE]Cl-MgCl2-H2O system was developed on the basis of the electrolyte nonrandom two-liquid (ENRTL) activity coefficient model embedded in Aspen Plus. The solubility of [HAE]Cl in water and magnesium chloride solutions over the temperature range from 277 to 370 K was measured by use of the dynamic method. With the equilibrium constant of [HAE]Cl obtained using experimental solubility of [HAE]Cl in water and the phase equilibrium equation, the new ENRTL parameters were obtained by regressing the solubility data for the two binary systems [HAE]Cl-H2O and MgCl2-H2O and the one ternary system [HAE]Cl-MgCl2-H2O at MgCl2 concentrations of 0.51 and 2.17 mol.kg(-1). These obtained parameters could accurately predict the solubility for the ternary [HAE]Cl-MgCl2-H2O system at MgCl2 concentrations of 1.05, 1.56, 2.72, 3.21, 3.87, 4.32, and 5.05 mol.kg(-1). The values at multiple saturated points at 298.15 and 323.15 K were accurately predicted with help of the newly developed model. The behavior of the ternary [HAE]Cl-MgCl2-H2O system at the two temperatures are successfully visualized with lucidity on an equilateral triangle. All of these will provide a thermodynamic basis for the preparation of the [HAE]Cl center dot MgCl2 center dot 6H(2)O complex.