Abstract: Corrosion perforation occurred on the weld inner wall of a Φ108 mm×5 mm sewage pipeline in an oil field.The analysis of macromorphology, chemical composition, metallographic structure of pipeline, XRD analysis of inner wall extract, SEM scanning microscope analysis of fracture, energy spectrum analysis and water sample analysis were carried out.The results show that oxygen corrosion is the type of local corrosion of weld, and corrosion under scale is the main cause of local corrosion of weld.Compared with that of the base metal, the corrosion resistance of the weld is worse, the corrosion product film is more loose.The turbulence caused by weld reinforcement and the high chloride ion content promote the local corrosion of the weld area of the sewage pipeline.