A there-dimensional finite element model of the working device of a single backhoe-bucket hydraulic excavator was developed to analyze and evaluate the rationality of structure design of the working device in this study. By finite element modal analysis, the resonant frequencies and vibration modes of the working device system were obtained. By dynamic response analysis, the changing trends of stress and strain of the device were obtained. In addition, the influence of different excavating resistance forces to the working device on dynamic response of the device system was compared for large and small resistance forces at the beginning excavation moment. The results show that a large resistance force at the initial excavating moment may result in the device vibrating with large vibration amplitude at the beginning excavation moment. These results might provide useful reference on design improvement of the excavator working device.