Abstract: Manufacturing technology and key points of valve spring were summarized. The cases of spring fracture caused by inclusions of spring wire, surface cracks of spring wire, surface extrusion during coiling spring and wear between adjacent rings at the end were introduced. The results of failure analysis showed that the main reason for the fracture of valve spring were the low purity of material and the defects on the surface of spring wire. The surface defects of spring wire came not only from the spring wire itself, but also from the manufacturing and assembly links. When analyzing the failure cases of spring fracture, the method of combining fracture analysis with field investigation could be used to accurately judge the cause, and measures could be taken quickly to avoid the recurrence of fracture problems.