In order to realize the comprehensive digging performance evaluation of hydraulic excavator,a research method based on the dimension variation factors of the working device is proposed. Using the digging range and digging force as the research objects,and considering the arm digging and the bucket digging in the digging operations. The working device size of excavator with similar weight are selected,and the comprehensive performance analysis is carried out under factors of boom,arm and bucket. According to the simulation software,the envelope diagram is drawn. The digging working dimensions and digging forces of each oil cylinder are obtained. Taking a excavator with similar tonnage as an example,the influence of each size of the working device on the digging performance is verified. The research results show that coordinate system transformation method is used to establish the coordinate system and calculate the digging envelope,and the tendency of the working dimensions of the simulation in each group is consistent with the theory. A digging force calculation model is built to compare each group digging force tendency. In the arm digging,with the change of the arm size,the change rate of maximum digging force of arm is 10. 3%. In the bucket digging,with the change of the bucket size,the change rate of maximum digging force of bucket is 11. 8%. The comprehensive digging performance analysis method for the design of the working device has important significance.