According to the partial homogenization and total homogenization features of the CO2—H2O system during heating process, we 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.. Following this law, we adjust the approximately measured filling factor of the fluid inclusion using an iteration method until getting a same molar volume. At the same time, the accurate filling factor value is obtained. With this value, the molar fraction of CO2 rich phase, total homogenization pressure, overall molar volume and other relevant parameters can be obtained. Other thermodynamic parameters, such as molar fraction of CO2 rich phase, total homogenization pressure, overall molar volume, can also be gained based on the accurate filling factor value calculated. A new software based on this method is developed, which can be applied to the CO2—H2O system at T<623.15K, P<100MPa 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%.