Abstract: Abstract: The domestic potato planting shows the main characteristics that it is distributed in scattered plots and hilly mountains regions with less acreage in the south of China. For some large foreign potato harvesters can be used in only few areas. According to the characteristics of domestic potato planting, the most way of harvesting potato is two-stage harvesting, so the digging model of potato harvester is common in the domestic potato diggers and is used in most areas in China. According to the regional users' feedback information and related field trials, it was found that problems of soil plug and weeds winding often appeared in the process of harvesting, and phenomenon of soil plug was more serious especially in northern cohesive soil. In the north, most of heavy soil not only restricts the development of potato harvest mechanization but also causes the damage of equipment and hence directly affects harvesting efficiency. Soil separation effect of chain elevator parts of potato digger is poor. The technology to prevent weeds winding, soil plug, jams, failure rate and mechanical damage is backward, which causes the damage to machines and tools and affects the efficiency of potato harvest greatly. It can not meet the requirement of the production of heavy soil, and severely restricts the healthy development of potato industry in the regions with heavy soil. So measures should be taken to improve the present situation. There are a lot of potato digger models in domestic, but afore-mentioned problems are almost universal. So designing a machine which can solve the soil plug of potato harvester and weeds winding around on the machine is very necessary. This paper aimed at the problems of chain elevator potato harvester in the process of potato two-stage harvesting, i.e. great resistance, failure rate, high mechanical damage rate and some key technical problems, and the 4U2A type of potato digger was designed. The harvester's structure and working principle were illustrated and its anti-blockage mechanism was theoretically analyzed, which consists of digging shovel, stone gate, front wheel, wheel for pressure grass and chain elevator, and the performance of the whole machine was tested at last. To obtain specific performance parameters, the machine was compared with the old one. The performance indices (obvious rate, injury rate, abrasion rate and productivity) in harvesting of this machine were 98.8%, 0.76%, 1.02% and 0.51 hm2/h, better than the old one (92.21%, 4.92%, 8.45%, and 0.31 hm2/h). Experiment results show that this machine solves the potato harvester's problems such as great resistance, high failure rate, grass winding, jams and soil plug in the process, which not only reduces the energy consumption of the tractor and machine failure rate, improves the efficiency and quality of potato harvest, but also provides the reference for solving the problem of anti-blocking mechanism design of potato harvest machinery. It is helpful for farmers to solve problems encountered in the process of the harvest and promote the development of potato production mechanization in China.