Abstract: In order to solve the problem of safety accidents caused by the loosening and failure of the anchor bolts of the head of the underground belt conveyor under long-term dynamic load, firstly, the failure mechanism of the anchor bolts is analyzed based on the horizontal force of the bottom plate and concrete, and the stress model of the head of the belt conveyor is established. Secondly, the stress balance of the head is analyzed, and the preload of the anchor bolts is determined, Finally, the numerical simulation software is used to study the influence of different diameter anchor bolts on the stress distribution and displacement of the bottom plate, and further determine the reasonable anchor bolt diameter parameters of the head anchorage. Through gmy400 anchor (cable) dynamometer, the fastening force of anchor bolt is monitored and statistically analyzed, and the rationality of selecting diameter is determined. The research shows that: in order to maximize the anchoring performance, the diameter of anchor bolt and the thickness of concrete wall should be comprehensively considered when anchoring. The field practice shows that selecting a reasonable diameter of anchor bolt can effectively reduce the loss of fastening force, improve the anchoring effect of anchor bolt and prevent the occurrence of head instability accident.