Taking capacitive MEMS accelerometer as the research object, the key degradation mechanisms such as fatigue and plastic deformation of MEMS accelerometer under vibration environment were analyzed theoretically. The fatigue reliability model was established based on Miner''s theory and S-N curve. The reliability model of plastic deformation was established based on the stress intensity interference theory considering the strength degradation. The Monte Carlo simulation method was used to verify the accuracy of these two degradation failure models, and the influence of key parameters on the reliability of the models was analyzed. The results showed 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 MEMS accelerometer.