Abstract: The early fatigue fracture of band springs appeared in the road testing and the fracture reasons were analyzed by means of chemical composition analysis,hardness measurement,fracture analysis and metallographic examination. The results showed that welding spatter would form a series of micropores and quenching marstensite and quenching cracks as a result of burning. Accordingly,the obtained stress concentration was the original fatigue source. Under the function of stress alternation,the micro crack expanded until fracture.