According to the partial homogenization and total homogenization features of the CO2-H2O system during heating process, the authors establish a thermodynamic model based on the latest thermodynamic parameters and related models. The molar volumes of the same one fluid inclusion are nearly same in partial homogenization state and total homogenization state. A new software based on this method is developed, which can be applied to the CO2-H2O system at T<623.15 K, P<100 MPa with total homogenization to liquid phase or critical phase. Comparative studies show that the software can also be extended to low salinity (<6%) CO2-H2O system within a relative error of 10%.