In the operation of bulldozer, the working device bears various complex loads, which raise higher demands on the rationality of the structural design, the convenience of the operation, the durability and the reliability of the working device. The finite element method is used to analysis the structural strength and the fatigue life of the working device. The dangerous points, stress, strain distribution and allowed cycle number were analyzed in two unfavorable working conditions and calculation conditions. The performance of working device was improved by changing the critical structural dimension. Then the structural strength and fatigue life of the improved blade structural were analyzed. Finally, the simulation results show that the improved working device can meet the dynamic load working requirements.