Abstract: Wave trap hanging ring was fractured abnormally with small stress in a transforming plant.Thefracture reason was analyzed by means of macroscopical examination, scanning electronic microscope and energyspectrometer analysis, metallographic examination.The results showed that fatigue fracture occurred in hangingring, and the fracture source on the surface of hanging ring where mechanical impairment and stress concentrationcan be found.Many inclusion and intergranular precipitated phase in the material further reduced its fatiguestrength.All of these induced the fracture of hanging ring in the end.