A series of thermodynamic functions are applied to generalize the Benedict- Webb-Rubin equation. The method has been successfully applied to this equation, which reduced the constants of BWR equation from eight to one. The calculation of PVT behavior of water over the entire thermodynamic surface is successful with satisfactory deviation. A series of thermodynamic functions are applied to generalize the Benedict-Webb-Rubin equation. The method has been successfully applied to this equation, which reduced the constants of BWR equation from eight to one. The calculation of PVT behavior of water over the entire thermodynamic surface is successful with satisfactory deviation.