Objective To analyze the main causes of oil pipeline corrosion leakage. Methods An investigation research on the accident was developed and the samples of perforation leakage were analyzed. Perforation morphology, geometric parameters, physical and chemical properties and microstructure were analyzed. Samples taken at the leakage and perforation point were analyzed by electron microscope scanning and EDAX. Results Chemical analysis and physical and chemical inspection for mechanical property and microstructure showed that the physicochemical properties of oil pipeline met GB/T 8163—2008 requirements and user requirements. According to the macroscopic pattern of perforation point, the pipeline with large corrosion area contains a lot of corrosion products on macroscopical analysis. A lot of critical corrosion pits are located in the lower part of the pipe and the maximum corrosion depth reaches 3.5 mm. The pipeline surface was covered with loose corrosion products under the electron microscope. They contained lots of Cl, C, O and Fe elements by EDAX analysis. Conclusion Material performance is not the main cause of failure accidents. The main cause of oil pipeline leakage is corrosion perforation. The main factor of corrosion perforation lies in the high Cl? fluid. When Fe from matrix is constantly dissolved and migrated by Cl? fluid, the corrosion pits will develop rapidly and lead to corrosion perforation eventually.