Abstract: There were many corrosion and perforation in L80 steel oil pipe of an oil well. By means of macroscopic observation, chemical composition analysis, energy spectrum analysis and phase analysis, the causes of oil pipe corrosion and perforation were analyzed. The results show that under the combined action of CO₂ corrosion, H₂S corrosion and under-deposit corrosion, the outer wall of L80 steel oil pipe formed non dense corrosion products, the H⁺, Cl^-, F^- contained in residual acid after acidification accelerated the corrosion process, and corrosion pits were formed on the outer wall of oil pipe. After the pipe wall of the oil pipe was corroded, under the action of the fluid column pressure of the oil well, the loose corrosion products fell off, and corrosion holes in the pipe were formed until the corrosion was perforated.