In order to study the fatigue life of the lift mechanism of mining wrecker and optimize the design of the weak part, a model of a rigid-flexible coupling system was established by integrating multi-body dynamic simulation and finite element method. Regarding dynamic analysis results as the random load of fatigue life analysis of lift mechanism, fatigue life contours were obtained and the minimum life was low. Based on SIMP method, topology optimization of lift mechanism was studied, and the multi-stiffness of static and eigenfrequencies were regarded as the optimization objectives. Then, the size optimization of the lift mechanism was studied. Compared with the stiffness and fatigue life of original lift institution, the performances of optimized structure are improved by 11.7% and 521%, which provides reference and basis for the design of the mining wrecker lift institution.