Abstract: The corrosion environment of oil wells becomes more and more complicated with the deep development of oil and gas fields. It is of great significance to clarify the failure mechanism of pipe materials in complex corrosion environments to ensure the safe and stable production of oil fields.The failure mechanism of an oil well pipe in Tahe Oilfield with the coupling corrosion environment of H₂S/CO₂/high salinity was studied by combining physical and chemical properties testing,finite element analysis and SEM, EDS and XRD. The results show that the physical and chemical properties of the pipe meet the standard, but the stress concentration generates in the transition zone causing the risk of stress corrosion cracking. The H₂S,CO₂, Cl^- and scale coating cause local corrosion and produce a large amount of H⁺. The penetration of H⁺ into the depth of the corrosion holes cause the embrittlement of the corrosion front. The expand of the corrosion microcracks cause the cracking under the effect of stress. The failure mechanism belongs to the coupling mechanism of local corrosion and stress corrosion.Pipes working under such conditions should pay attention to reasonable structural design and regularly add corrosion and scale inhibitors to avoid the recurrence of similar failures.