Abstract: Rotating shaft subassembly of electric locomotive happened to fracture abnormally at early stage. The fracture reason was researched by means of macroscopical and microscopical analysis. The results showed that localized corrosion cracking and fatigue expansion occurred in rotating shaft subassembly under the combined action of erosive environment and cyclic stress. The fracture of rotating shaft subassembly was corrosion fatigue fracture, and rotating shaft was ruptured earlier than that in the interior pinion shaft.