In the process of CO2 flooding，CO2 can change the physical properties of oil by dissolving into the oil，thereby improving the oil recovery factor. However，the effects of temperature and injection pressure on the displacement efficiency and the change rules of the oil properties in the process need further research. It was studied through rock displacement ex? periments and oil physical properties testing experiments. The results show that the oil recovery factor remains almost un? changed as the injection pressure increases under 22 ℃. While the effect of injection pressure on the oil recovery factor is limited when the injected CO2 is in gas state under 60 ℃. However，when the injection pressure increases to a point at which the CO2 is in supercritical sate，the oil recovery factor will be largely improved，but the gas to oil exchange ratio will decrease quickly. And when the injection pressure increases to the minimum miscible pressure，the growth of oil recovery factor slows down. The CO2 breakthrough is more likely to occur when the CO2 is in gas state than in supercritical or liquid state. The analysis of oil physical properties shows that the produced oil becomes lighter and its density and viscosity de? crease with the increase of production time and injection pressure at constant temperature.