Under the national strategy of carbon peak and carbon neutrality in China,utilizing CO₂ for enhanced oil recovery becomes an important means of CO₂ storage in oilfields. However, there are still challenges in the safe storage and transportation of liquid CO₂,in which gas impurities have a great influence on the thermodynamic properties of liquid CO₂.Seven common gas impurities were determined by the analysis of CO₂ samples obtained in the field,and the changes in physical properties of the CO₂ samples containing impurities were simulated by HYSYS and the molecular dynamics simulation method.The physical property diagrams were plotted and compared with those of pure CO₂.The results reveal that all seven impurities can enlarge the gas?liquid coexisting region in CO₂ phase diagrams,but the enlargement extent differs. The impurities mainly expand the gas?liquid coexisting region by changing the bubble point line,while the dew point line has little change.It is found by molecular dynamics simulation that the electrostatic potential energy plays a dominant role in the CO₂ mixture containing C₂H₆,C₃H₈,and C₂H₄.Therefore,compared with the results of the mixture containing H₂,CO,CH₄,and carbonyl sulfur (OCS),its macroscopic physical properties are less affected by temperature and pressure fluctuations.