In this paper, we focused on the correlation of the thermodynamic properties of aqueous solutions across a temperature range from (273.15 to 523.15) K by a simple two-parameter model. This model is based on the modified three-characteristic-parameter correlation (TCPC) model. The two parameters, b, distance of closest approach, and S, solvation parameter, represent the interactions between ions and ions-molecules, respectively. The results show that it can adequately correlate the activity coefficient and osmotic coefficient of the single electrolyte solutions. The set of two characteristic parameters for many electrolytes was obtained. We also obtained the temperature-dependent parameters for these electrolytes. In over 70 % of the cases, six to eight parameters are necessary for an electrolyte. Compared with the Pitzer model, our model also represented a good performance.