Hydraulic faceshovel excavator of work unit was based on as the research object. Through the DH method, modeling analysis of excavator working device was carried out, and the bucket volume of 36 m3 of a type of faceshovel working device was optimized in design. The determination of the objective function was described in detail, as well as the determination of design variables and constraints. It was gotten the optimized shovel and the location of the solution trajectory, digging bucket envelope and angle in the process of peaceful shovel and distance of peaceful peace from the contrast of the image. It was carried on the analysis and comparison, and proved of the rationality of optimum design.