Abstract: Aiming at the cascade failure of complex mechanical systems, a new quantitative analysis method was put forward to investigate their failure mechanism. By analyzing the conversion relationship of components in mechanical systemsduring cascading failure, a failure mechanism model for complex mechanical systems was established. Mathematical theory deduction was carried out on the model, and conversion relationshiptheories of components in complex mechanical systems were established. The influence of influence rate, maintenance rate, repair rate andconversion rate on the failure of components in complex mechanical systems was studied by simulation with MATLAB, including the influence of the four parameters on potential failure components and the real time change trend of failure components. The results show that influence rate and repair rate are main influencing factors for failure of system components. There is a positive correlation between the failure of system components and influence rate, conversion rate, but there is a negative correlation between the failure of system components and repair rate, maintenance rate. Before the proportion of failure components in the total components arrives at its highest point, some measures should be taken to reduceinfluence rate and conversion rate and increase repair rate and maintenance rate.