The blade in the installation of test failed in the operating process,fault location is located in the root of blade.Through observation,testing and analysis of fault component,the reason blade produced by low cycle fatigue fracture is identified due to improper control of production process.The blade root curing is incomplete in local area,which causes the strength and stiffness of very low. Fiber beam between curing not completely of resin cannot will load effective of passed to near of fiber beam, so dang by fatigue load role in structure stress concentrated regional first occurred layered cracking, and extended until eventually lost stability fracture.The direction for improvement is pointed out.