The study of the solid-liquid phase equilibrium for (NaCl + NaClO3 + H2O) system is of significance to understand the thermodynamic property of the aqueous solution of ionic membrane electrolysis process to promote the production of sodium hydroxide (caustic soda). The solubilities and the physicochemical properties including density, refractive index and pH for this ternary system at 293.15 and 333.15 K and 0.1 MPa were measured using the isothermal dissolution method. Based on Pitzer ion-interaction model and its extended HW model, the solubility equilibrium constants Ksp of NaClO3 and the mixing ioninteraction parameters (theta(Cl,ClO3), Psi(Na), (Cl,ClO3)) at 293.15 and 333.15 K were parameterized in this work. The Debye-Huckel limiting slope (A)empty set)), the Pitzer single-salt parameters of NaCl and NaClO3 and the solubility equilibrium constants Ksp of NaCl at 293.15 and 333.15 K were taken from the relative temperature-dependence formula in the literature. A comparison shows that the calculated solubilities of the ternary system at 293.15 and 333.15 K agree well with the experimental data. The calculated results of densities and refractive indices using the empirical equations agree well with the experimental data at 293.15 and 333.15 K. (C) 2018 Elsevier Ltd.