A new perturbation method for electrolyte solutions is given in our recent paper (Wu, J.Z., Lu, J.F. and Li, Y.G., 1994. Fluid Phase Equilibria). Here we apply this model to pure water and real electrolyte solutions. Equations of state for water and eletrolyte solutions are further developed. The parameters of water are obtained by fitting the saturated vapor presssure and liquid density experimental data simultaneously over st wide range of temperature. With these parameters of water and Pauling radii of ions, the densities of single electrolyte aqueous solutions can be predicted for the concentration range up to saturation at temperature of 25 degrees C without any adjustable parameters.