Taking the cantilever structure of capacitive MEMS accelerometer as the research object, the typical failure mode and failure mechanism of MEMS accelerometer in vibration environment were analyzed. Based on Miner′s theory, the stress-life curve was introduced to establish the fatigue reliability model. The reliability model of plastic deformation was established based on stress intensity interference theory considering strength degradation. The Monte Carlo method was used to verify the accuracy of the two reliability models, and the influence of the key parameters of the model on the reliability was analyzed. The results show that the vibration stress level and the yield strength of the material had significant influence on the reliability. Reducing the stress amplitude and increasing the yield strength can improve the reliability of the MEMS accelerometer.