Abstract: Abstract: The vibration damping spring of  65Mn Steel broke after one year of use。The fracture causes of spring were analyzed by means of macro analysis, chemical composition analysis, hardness test, metallographic analysis and fracture micro analysis. The results show that the oxide skin on the surface of the billet is not cleaned, and the folding and micro cracks are formed in the drawing process. Under the action of alternating load, the cracks continue to expand, and finally the spring has fatigue fracture.