In order to solve the problem of low efficiency caused by stoppage unloading during field operation of bagging potato combine, a non-stoppage unloading device was designed. The device can switch between caching and bagging status, and achieve non-stop unloading during the machine operation process. The expression of the maximum contact stress during the collision between potato and potato box was derived by using Hertz contact theory, and the key factors affecting the contact stress were obtained. An analysis was conducted on the unloading process of the unloading device, and the size parameters of the unloading device were determined. Three possible motion directions of the potato after collision with the wall of the box were analyzed by the velocity vector diagram. Based on the principle of kinematics, the trajectory and velocity expression of potato in the falling process were defined, and the key factors affecting the potato speed were obtained. In order to determine the best structural parameters of the box, Box-Benhnken test method was used to carry out three-factor and threelevel tests on the device with wall angle, conveyor belt speed and box wall length as test factors and potato peel breakage rate and potato damage rate as test indexes. Analysis of variance was performed on the test results through Design-Expert 11.1.0 software to identify the factors that had a significant impact on the experimental indicators, and the rule of influence of experimental interaction factors on test indicators was analyzed through response surface tests, and the optimal structural parameters were obtained. On this basis, experimental verification was carried out, and field comparison experiments were conducted. The bench test showed that when the wall angle of the potato box was 44°, the sorting and conveying chain speed was 0.44m/s, and the wall length of the potato box was 603mm, the breaking rate was 0.96% and the damaged rate was 0.63%. The results of field comparative experiment showed that the obtained data met the operational requirements of the potato combine harvester and the harvesting efficiency was improved by 41.63% compared with that of shutdown unloading combine harvester.