Abstract: Abstract: At present, the sugar beet harvest is still hand operation in China, which results in labor intensity and low efficiency. Therefore, the development of sugar beet harvester is an efficient approach to change the traditional way of harvesting sugar beet in China. Since harvesting is the crucial process, the harvest device has played important role in the process of the sugar beet harvest. The digging component is a major operating unit of harvest machine and it can influence the harvest performance, working resistance and power consumption of machine directly. As such the digging device is the bottleneck of the development of mechanization for sugar beet harvesting. As a sugar beet harvester machine, a disc type digging device that can break and turn soil, and separate sugar beet from soil completely, has some advantages for its simple structure, less digging volume, small digging resistance. In addition, it can also reduce harvest time and labors. All of those give disc type digging device a great superiority in the field of the digging device of harvest machine. To solve the problem of harvest blocking, the performance parameters of disc digging device were obtained by combining the structure and working principle, which affected its adaptability and stability, such as opening angle, deflection angle and digging depth. And the motion equation of disc blade was set by analyzing the relationship between the parameters and movement mechanism of the digging system theoretically. In order to design a more reasonable digging device with better digging effect for the disc type digging harvester of sugar beet, an orthogonal experiment and weighted score method were carried out. The comprehensive score index was an important technical index to be considered for the overall performance, and factors directly affecting the overall performance included clay content, break rate and damage rate. To improve the working performance of disc type digging device, three variables were selected as the experimental factors, i.e. opening angle, the deflection angle and digging depth of digging device. With three factors and three levels orthogonal experiment, the influences of each factor on the harvest performance were reported, and optimal technique parameters were obtained. The results showed there was a large influence of digging depth on clay content and break rate, and an interaction influence of opening angle and digging depth on the break rate for sugar beet, while no significant influence of deflection angle on these two indicators. However, there was a negligible effect on damage rate from each factor. With the opening angle of 15 °, the deflection angle of 35 ° and digging depth of 90 mm, the clay rates of sugar beet was 2.7%. There was no break or damage for sugar beet, with the opening angle of 19 °, the deflection angle of 30 ° and digging depth of 120 mm. For many indicators, comparative analysis was used by synthetically judgment, which was an important method of economic analysis for the agricultural technology. There was a significant effect on comprehensive score index from opening angle, digging depth and those interaction term. The optimum working conditions were: opening angle 15°, deflection angle 30°, and digging depth 120 mm. The research can provide references on optimizing the harvester machine structure, and improving the performance of digging device.