Abstract: A kind of bolt for connecting traction saddle and corrugation of a vehicle model fractured during static commissioning after installation and tightening. The fracture causes of the bolt were analyzed by means of fracture analysis, chemical composition analysis, residual hydrogen detection analysis, mechanical property testing and metallographic examination. The results show that the fracture mode of the bolt was hydrogen induced brittle fracture. It was recommended to remove hydrogen in time during the bolt manufacturing.