Abstract: Corrosion leakage occurred in the coil of single well water jacket heating furnace in an oilfield during service. Macroscopic observation, chemical composition analysis, metallographic examination, scanning electron microscope and corrosion product analysis were used to analyze the corrosion causes of the coil. The results show that the main cause of coil corrosion was dissolved oxygen corrosion in high temperature water bath, accompanied by steam water corrosion caused by metal overheating under scale.