Abstract: Different from the mechanism of improving light oil recovery by CO₂ injection, heavy oil does not mix with CO₂, so the main factors affecting its development are very different. Especially in the process of thermochemical composite oil recovery, the injected CO₂ mainly plays a role in insulating heat, reducing viscosity and increasing energy. The properties of heavy oil were determined in this study in order to systematically investigate the effects of different factors influencing CO₂ displacement. The effect of heavy oil viscosity, temperature, pressure and permeability on recovery were investigated using the orthogonal experimental method. Temperature was the most significant factor, followed by permeability, pressure and heavy oil viscosity. According to the experimental results and considering factors such as reservoir temperature and permeability, the field tests of CO₂ huff and puff in the Shengli Oilfield of SINOPEC were conducted. Production results show that increasing reservoir temperature and permeability is beneficial for CO₂ EOR and can improve oil production.