Abstract: Hydrogenation recycle compressor is the key power equipment in hydrogenated unit.The piston rod fracture is the main failure form in the process of hydrogenation recycle hydrogen compressor operation, and the causes of failure are often different.According to different situations of the piston rod failure cause, avoiding the failure of hydrogenation plant is of great significance to the safe operation of unit.In view of the fracture failure of the piston rod of a hydrogen cycle compressor, the macro and micro structure morphology observation, chemical composition analysis and section hardness test of the broken piston rod were carried out to gradually clarify the cause of the fracture failure of the piston rod.The results show that the microstructure of the piston rod conforms to the standard, and the fracture surface has no typical characteristics of fatigue fracture and stress corrosion fracture, which is caused by hydrogen infiltration into the metal.