Abstract: The corrosion caused by the coexistence of oxygen and carbon dioxide has become the main cause of metal material damage in oilfield injection well conditions. The corrosion behavior of P110 and 3Cr oil pipe steels in a high salinity reservoir water environment with high temperature, high pressure, and O₂-CO₂ coexistence was studied by simulating the injection well operating conditions (O₂-CO₂ coexistence environment) in a western oilfield using a high temperature and high presure reactor. Corrosion weight loss testing, three-dimensional morphology analysis of pitting corrosion, and microscopic analysis of corrosion products were also conducted. The results show that the two types of oil pipe steels suffered severe uniform corrosion and localized corrosion in an environment where O₂ and CO₂ coexisted. Within the temperature range of 90-150 °C, the corrosion of the two materials intensified with increasing temperature, with a uniform corrosion rate increase of 79.7% and a maximum pitting corrosion rate increase of 143.4%. When O₂ and CO₂ coexisted, the cathodic reaction significantly accelerated, accelerating the formation of poorly protected iron oxides, leading to severe uniform corrosion and localized corrosion. However, the content of Cr in low Cr steel was not sufficient to improve the protection of the corrosion product film. So the low Cr steel could not adapt to the environment where O₂ and CO₂ coexisted.