Natural gas hydrate replacement model failed to accurately analyze the influence of temperature on the degree of substitution of the replacement of existing carbon dioxide extraction. Besides, the compression factor is not precise enough when calculation of gas volume is being performed under high pressure, which leads to big error to the calculation of model. The experimental conditions under the principle of isovolumic synthesis, replacement system containing the gas state equation and multicomponent thermodynamic phase equilibrium principle based on the consideration of high pressure carbon dioxide and methane solubility equilibrium in water, the compression factor calculation method was optimized, and the model for methane gas and the temperature in reaction was established, the definition was made for the replacement of the amount of carbon dioxide replacement efficiency divided by the amount involved in the synthesis of methane, and the relationship model for the replacement efficiency and temperature influence was further deduced. The comparison between calculation results of the model and isovolumic synthesis experiment data published in literature shows that the model has comparatively high calculation accuracy.