Abstract: The causes of fracture failure of a marine stern shaft were analyzed by macroscopic analysis, chemical composition analysis, mechanical property test, metallographic examination, fracture scanning electron microscopy analysis and energy spectrum analysis. The results show that both the chemical compositions and the mechanical properties of the marine stern shaft met the requirements of relevant standards and specifications, and the microstructure was normal ferrite+pearlite. The fracture morphology had fatigue fracture characteristics, and the galvanic corrosion fatigue was the main cause for the fracture of the marine stern shaft.