Abstract: The early fracture failure occurred to a valve spring of the gasoline engine during the bench test. The failure reasons of the valve spring were analyzed by means of fracture observation and analysis, chemical composition analysis, metallographic examination and hardness testing. The results show that:the fracture mechanism of the valve spring was fatigue fracture; the fracture reason of the valve spring was that the abrasion existed on the surface and reduced the fatigue strength and the fatigue life of the valve spring.