Abstract: Bolt fasteners are related to the safe operation of equipment, and it is necessary to analyze the failure reasons of bolt fasteners. The fracture phenomena of 20Cr13 martensitic stainless steel bolts for marine equipment are analyzed comprehensively by means of macroscopic morphology, chemical composition analysis, mechanical property test, microstructure, fracture morphology observation and energy spectrum analysis of the corrosion products. The results show that the tempering brittleness of 20Cr13 steel treated at low temperature increases and the hardness exceeds the standard. Under seawater environment and stress, pitting corrosion and crevice corrosion occur on the surfaces of bolts and cause micro-cracks, eventually leading to stress corrosion fracture.