The cyclic loading generated under multi-stage fracturing conditions can lead to frequent occurrence of cement ring sealing failure events, which seriously affects the safe development of shale gas wells, so it is particularly important to carry out the research on cement ring sealing failure under cyclic loading conditions.Based on the cohesive unit damage model, simulate the size of the gap on the cemented surface of ‘cement ring-casing’, and establish the ‘casing-cement ring-strata’ three-dimensional finite element model. The three-dimensional finite element model is used to investigate the influence of the parameters of cement ring, the internal pressure and the number of cycles on the stress distribution of cement ring under the joint action of the ground load and the internal pressure, and finally, the plastic damage volume is used to simulate the damage of the cement ring body, so as to clarify the mechanism of the sealing failure of cement ring.The results show: Pressure changes within the casing cause the cement ring to lose its sealing effect and create a micro-annular gap at the first and second interfaces. The cohesive damage unit begins to fail on the first load cycle, with the initial cement surface displacement increasing as the number of load cycles increases; thus, the cohesive damage unit begins to fail on the first load cycle and the initial cement surface displacement increases as the number of load cycles increases;Under the same cyclic loading condition, the plastic deformation of the cement ring is exacerbated to some extent as the modulus of elasticity of the ring increases.Therefore, appropriate control of cement ring elastic modulus and the number of cycles can effectively reduce the risk of cement ring failure and provide an important guarantee for the accurate evaluation of cement ring sealing.