To better investigate the thermodynamic and kinetic features of the methane replacement process, this study established the phase equilibrium conditions of compound hydrate production and gas capture in mixed gas CO2N2 with the CO2 concentration of 40%, 50%, and 70%. The results revealed that the hydrate formation circumstances in the mixed gas were gentler, and the experiment with CO2-N2 (50/50 vol percent) produced the lowest concentration of CO2 in the gaseous phase that stayed above hydrate. In this study, as the N2 concentration in the mixture decreased, the capture rate of N2 and CO2 increased, as did the recovery of CH4. Finally, the highest percentage of CO2 captured from the gaseous phase reached up to 96.3% and CH4 recovered from the solid phase reached 48.44% when the CO2/N2 70-30 vol% flue-gas was used.