Abstract: The high strength stud was fractured after 10 months of service. The causes of stud fracture were studied by means of macroscopic observation, chemical composition analysis, scanning electron microscope analysis, metallographic examination and mechanical property test. The results show that under the action of large alternating load, cracks initiated and propagated at the folding position of the screw thread bottom of the fractured stud, and finally fatigue fracture occured.