Abstract: Abstract: The development of garlic harvest mechanization still lags relatively behind, restricting the development of China's garlic industry. In recent years, garlic combine harvester has been designed by Chinese research institutes, realizing the garlic digging, soil cleaning, stalk cutting and garlic bulb gathering. The main garlic combine harvester in the developed countries is bundling type or cutting seedling type harvester. The garlic combine harvester, which can finish the processes of root cutting, is few. Root cutting is the core technology of garlic harvest, and also the most difficult technical operation. The fresh garlic has thin and tender skin and different size, and its roots are mixed with sediment, which have a wide but disorderly distribution. Therefore, in the process of harvesting, how to ensure technical performance, such as high rate of one-time root clearance and low rate of bulb damage, has been a difficult technical problem of garlic root cutting mechanized operation. In view of the lower rate of root clearance and the higher damage ratio, a root cutting device of garlic combine harvester was designed, which realized the root cleaning and pre-cutting, the garlic sorting and arraying, and the second cutting of root. The root cutting device of garlic combine harvester consists of clamping delivery device, hairbrush roller, front revolving cutter, rank-alignment device and floating cutting device. The clamping delivery device carries out the clamping of garlic upper stalk and the transport. The clamping style of garlic is changed from chain-chain clamping to chain-board-hairbrush clamping. The rank-alignment device mainly achieves the functions of stalk fixation and garlic bulb alignment, which provides ancillary work to root cutting. The floating cutting device adopts the principle of floating rotary cutting to adapt different sizes of garlic bulb, which can realize shape cutting along the spherical trajectory under the garlic bulb. The spiral protection railings are installed outside the cutter of floating cutting device, which stay on the outside of cutter turning trajectory and keep the free state. This structure reduces the impact force when garlic bulb contacts the spiral railings, and thus solves the problems of hurting garlic bulb effectively. Combining theoretical analysis with experimental research, this paper has determined the key structure parameters and the key working parameters, and at the same time, synthetically optimized the main factors affecting root cutting quality. The results showed that the importance sequence of various factors affecting root cutting quality was as follows: conveying speed > clamping angle > cutter rotational speed. Under the 95% confidence level, conveying speed was highly significant for root cutting quality; clamping angle and cutter rotational speed were significant for root cutting quality. The optimum parameters were that the conveying speed was 1.05 m/s, the clamping angle was 79°, and the floating cutter rotational speed was 2 200 r/min (The cutting linear velocity was 17.3 m/s). Under the conditions, the rate of cutting root was 96.1%, and the damage ratio of garlic bulb was 2.39%. The results provide the technical basis for the design and optimization of the root cutting device.