As one kind of green renewable energy, biogas has great significance in supplying energy utilization in the country. This work focuses on the research of capturing CO2 from biogas and transporting and storing the CH4 by hydrate method. Depending on the thermodynamic characteristics of CH4, CO2 when the temperature is above 283K, a new, one-step hydrate method biogas decarbonization, storage, and transportation process is processed in prior. Then the thermodynamic model for this system is developed. The energy parameter of water and CO2 are developed as a function of (1-(T/Tc)0.5), respectively. Then with the experimental data of gas-liquid solubility of CH4-H2O and CO2-H2O, the binary interaction parameter kij is re-fitted, respectively. With the re-fitted α, kij and the hydrate phase equilibrium conditions of CO2 and CH4, the Antoine constants in the Chen-Guo model are developed. For CO2, the influence of water activity coefficient and the segmentation are also considered. Based on comprehensive analysis, this work selects the segmented CO2 macropore Langmuir absorption coefficient ignoring pressure and the effect of CO2 on water activity. For biogas with CO2 concentrations ranging from 8% to 85% at a given temperature, the new thermodynamic model is used to calculate the phase equilibrium conditions. The results show that the average absolute error AAD is only 3.64%.