Abstract: The connecting studs of wind turbine blades in a wind farm were fractured. The fracture causes were analyzed by means of macroscopic observation, chemical composition analysis, metallographic examination, scanning electron microscope analysis, mechanical property test and field investigation. The results show that the assembly accuracy was insufficient in the installation stage of the stud, which led to the eccentricity of the stud, which made the stud contact with the hole wall of the stud, and the stress concentration occurred at the contact part. During the operation of the unit, the stud bore additional radial load, resulting in an increase in stress amplitude and a significant reduction in fatigue life. The application process of stud lubricant did not meet the specification requirements, resulting in the pre-tightening force failing to meet the design standard during construction, the fracture nature of the stud was fatigue fracture under alternating stress.