Abstract: The equation of state for aqueous electrolytes based on perturbation theory is simplified.By using the water molecule parameters and ionic diameters,the densities of 12 single aqueous electrolyte systems including strong acids,9 binary and 1 quaternary aqueous electrolyte systems at different temperatures are calculated.The correlation accuracy of densities is about 1% for single electrolyte aqueous and 2% for the prediction of densities of mixed electrolyte aqueous systems.The prediction accuracy can be improved by using the fitted cation diameter from the relevant single electrolyte systems instead of Pauling diameters.