Abstract: Abstract: Sugar beet is one of the most important sugar crops in China, which ranked second in terms of acreage, only after sugarcane. As a kind of seasonal operation, sugar beet harvesting in China is still mainly manual work, which constrains the further development of the sugar beet industry. Mechanized combine harvesting is the inevitable development trend of sugar beet harvesting. Guidance system is the major part of harvest machine, which can reduce the driver's labor intensity and beet's harvest damage in the harvest process. With the development of the technology of electronics, sensor and GPS guidance, the guide technology has been commercialized and applied to the field of agricultural equipment widely in the developed countries. The combine harvesting with the guide device is characterized by high automation and intelligence and advanced performance. However, the guide device is still in the stage of prototype development in China, and there is a great gap between domestic and advanced foreign technology. The research on beet's guiding harvest is scarce, and this restricts the quality of beet digging and mechanization. To solve the problem of the guide on-row harvest of disc type sugar beet harvester, the structure and working mechanism of the guiding system were determined on the basis of analyzing the existing technology and the structure. And the key parameters relating to the performance of guide mechanism were obtained based on its operating conditions and mechanical structure. Combined with the disc type digging method, a guiding system integrating mechanical and hydraulic guide technology was designed to realize the digging along planting row, which mainly consisted of hydraulic steering and direction detection parts. In the process of automatic guide on-row harvest, beet profile was taken as orientation marker, and the information was obtained by guiding detect pole. The real-time direction adjustment was conducted by cylinder's telescopic movement installed on traction frame, which made beet located in the digging scope all the time. Combined with the structure and working characteristics of the guide device, the load and movement characteristics of the guide mechanism were analyzed, the acceleration equation of the guide mechanism was obtained, and the key parameters relating to the performance of guide mechanism were summarized. Based on field experiment and response surface optimization method, the mathematical models of the key parameters and guide effect indices were established, the influence rule of parameters on the test index was studied, and the value range and the optimal combination of the parameters were determined. By field test of harvest performance, the working efficiency, suitability, reliability and other performances of the prototype were improved and the imperfection was perfected. The guide device had an ideal work effect when the bending angle was 145°, install angle was 8° and horizontal length was 240 mm. Conclusion was drawn according to field test: the system implemented the automatic guiding in the harvest process, and the loss rate was 5.12%, which met the harvest quality standard (NY/T 1412-2007). So the prototype has met the performance requirement of harvesting sugar beet. The results can provide the reference for similar harvester design and guiding harvest for other single root crop.