In response to the bottleneck issues of low impurity removal efficiency, difficulty in removing seedlings and vines, severe damage and bruising of potatoes and high cost of subsequent cleaning and impurity removal in existing potato combine harvesters, a bagging and unloading potato combine harvester was developed by an operation mode which was double sieve for potato-soil separation, plate device for picking potatoes, manual assisted sorting and automatic bagging and unloading. This machine was mainly composed of soil loosening and depth limiting device, soil cutting and vine cutting device, excavation device, primary sieve for separating potatoes and soil, manual auxiliary sorting platform, double-sieve device for separating potatoes and impurity, plate picking potatoes device, and potato bagging and unloading device. On the basis of elaborating on the overall structure and working principle of the harvester, the process of double sieve for separating potatoes and soil and plate picking potatoes were analyzed, the movement trajectory and impact characteristics of potatoes at the connection between the sorting conveyor sieve and the potato bagging and unloading device were clarified. The plate picking device could achieve the separation of potatoes and seedlings, which could reduce the loss rate. The technology of caching and bagging potatoes and unloading with gradually decreasing weight could achieve automatic switching between the caching and bagging status to ensure non-stop flexible potato harvesting and loss reduction unloading. The experimental results showed that at operating speeds of 3.01km/h and 3.95km/h, the productivity was 0.39hm2/h and 0.51hm2/h, the damage rate of potatoes was 1.68% and 1.44%, the bruising rate of potatoes was 2.05% and 1.71%, the impurity content rate was 1.75% and 1.96%, and the loss rate was 1.56% and 1.52%, respectively. All performance indicators met the requirements of relevant standards.