Abstract: The fracture phenomenon of a post pedestal anchor bolt was analyzed by means of macroscopic observation, chemical composition analysis, scanning electron microscope and energy spectrum analysis, metallographic examination and hardness test. The results show that the microstructure, thread surface continuity, mechanical properties and chemical composition of the anchor bolt were not abnormal. The fracture mode of the anchor bolt was fatigue fracture. The corrosion pit at the bottom of the threaded tooth aggravated the stress concentration at this part. Under the action of periodic load, the fatigue crack initiated and expanded, which eventually led to the fracture of the anchor bolt.