Abstract: The tubing of an oil well in western oilfield was corroded severely and even perforated. The cause of the tubing failure was analyzed by macroscopic morphology and microstructure observation, chemical composition analysis, hardness test, tensile and impact performance test, corrosion product detection. The results show that uniform corrosion and localized corrosion of the tubing occurred in the acidic environment containing Cl^-,H₂S and CO₂. The uniform corrosion occurred as a result of hydrogen evolution corrosion caused by the H₂S-CO₂-H₂O (Cl^-) system. The micro galvanic effect caused by the deposition of CaCO₃ and the hydration of Fe²⁺ and Cl^- in the formation water led to the localized corrosion and perforation of the tubing. It was suggested that P110-3Cr steel with certain sulfur resistance or steel with better corrosion resistance should be used for the oil well tubing materials, and corrosion and scale inhibitors should be added for protection.