Abstract: The springs fracture during the test of play to bolt. The means, such as chemical composition analysis, metallography and scanning eletron mircroscope etc, were used to analyse the springs. The result indicated: During removing hydrogen after cadmium plating the springs did not strictly execute technology, keeping a large amount of remanent hydrogen and dispersive distribution in the springs, and initiating crack along the grain boundary, which caused brittle fracture among grain boundary under applied force finally.