Abstract: Replacing methane with CO₂ in the hydrate structure, storing CO₂ and producing methane from methane hydrate reservoirs have attracted much attention of the researchers worldwide. The effects of pressure and temperature on replacement rate were investigated by measuring the change of the methane molar percentage in the gas phase. The test system was in pure water, and the replacement reaction lasted 50 hours. The experimental results show that the methane molar percentage in the gas phase at the end of replacement process is increased from the initial 1.56% to 39.74%, 41.89%, 45.45% and 48.04% respectively corresponding to the replacement temperature at 273.15 K, 274.15 K, 275.65 K and 276.15 K with the CO₂ charge pressure at 2.5 MPa. On the other hand, the replacement rate respectively reach 44.87%, 45.45%, 46.66% and 47.21% corresponding to the CO₂ charge pressure from 2.2 MPa to 2.5 MPa, 2.8 MPa, 3.1 MPa with the replacement temperature at 275.65 K. Therefore, it is concluded that the influence of temperature and pressure on replacement rate is positively in some ranges, but not great.