Based on the Pitzer and Harvie-Weare (HW) chemical model, the Pitzer models for the complex systems containing solid solutions were constructed by combining the equations for composition and solubility equilibrium constants of the solid solutions. According to the parameters, the composition of the solid solutions and the solubilities of the ternary systems NaCl-NaBr-H2O, KCl-KBr-H2O and Na+, K+ // Cl-, Br--H2O at 313 K, the composition equations and solubility equilibrium constant equations of the solid solutions were fitted in the present study. Then, the solubilities of the systems were calculated to evaluate the accuracy of the new method for the solubility calculation for the systems containing solid solution. Comparisons between the calculated and experimental solubilities show that the predicted data agree well with the experimental results.