Abstract: By means of high-pressure physical property experiment, group component analysis experiment and gas chromatography experiment, the influence of supercritical CO_2 on the physicochemical properties of heavy oil was analyzed. The results show that with the increase of injection of supercritical CO_2, the saturation pressure, gas oil ratio and volume expansion coefficient of heavy oil increase in quadratic polynomial relationship, and the injection of supercritical CO_2 can reduce the viscosity of heavy oil in quadratic polynomial relationship, thus effectively improving the physical properties of crude oil. With the increase of injection ratio of supercritical CO_2, the total hydrocarbon content of heavy oil is relatively increased, while the content of gum + asphaltene is relatively decreased. The supercritical CO_2 is highly selective for n-alkanes or components like n-alkanes in the extraction process of heavy oil total hydrocarbon components. Generally, the injection of supercritical CO_2 can effectively change the physical and chemical properties of crude oil, thus achieving the purpose of enhanced recovery.