This paper aims at the difficult problem of repairing and welding the oil leakage of locomotive oil tank in the locomotive depot,through the analysis of the defects which cause oil leakage of the oil tank and the site situation,we develop a reasonable welding process and implement it,then summarize a set of welding operation method for oil tank. The results show that the selection of the correct welding parameters,groove form,and the welding process of manual arc breaking arc welding repair welding oil tank can completely meet the requirements of tank structure design and operating.