Concerning the fatigue failure of the gear reducer for the large scale recreation facilities-large pendulum,the fatigue life of the non-uniformly distributed planetary gear of the large pendulum under cases of non-destructive and crack is studied. Some digitized models of planetary gear train with different cracks are built. Based on the theory of fracture mechanics,the relationship between the intensity factors of crack stress and the fatigue life of the gear is analyzed. By the combined using of ANSYS Workbench and nCode DesignLife,the stress variation and fatigue life of gear is obtained,and thus to verify whether the design could meet the mechanical design requirements and acquire the influence of the crack gear on the fatigue life of reducer.The results can be applied to structure optimization of reducer gear,manufacture and detection under operation.