A molecular thermodynamic model of polyelectrolyte developed previously was extended to polyelectrolyte solutions with added salts. Thermodynamic properties, such as activity coefficients of polyelectrolytes or added salts and osmotic coefficients of solvent, of a number of aqueous mixtures of polyelectrolytes and salts are analyzed with the proposed model, Successful correlation is obtained in the range of moderate or higher polyion concentration. For the same sample, thermodynamic properties of polyelectrolytes with and without simple electrolytes can be predicted mutually using parameters from regression data.