Abstract: Aimed at the existing problems revealed in a field test of 4UFD-1400 potato combine harvester, such as higher transmission speed, easy bruising on potato tuber epidermis, and blockade in potato conveying and grading bagging process, the transmission system, potato tuber conveying system, and stalk separating device of the machine were improved, and potato harvest experiments were conducted on parallel sowing dry land and double ridge sowing fully-mulching dry land. The results of field harvest contrast tests showed that the devices for soil separation, stalk separation, potato tuber conveying, grading and bagging of the improved machine work more stably and reliably compared to the original one. The improved machine exhibits good quality and adaptability to the potato harvest both in the parallel sowing dry land and double ridge sowing fully-mulching dry land, and also good ability for the separation of potato seedlings, weeds, and mulch films. It can work effectively in the conditions without clearing mulch films, potato seedlings, and weeds. The improved design of the potato vertical lifting device and additional design of a chain rod type horizontal conveying device for graded tubers effectively prevents potato tubers from stacking and being in the conveying process, and enhances the soil separation. The potato harvester enables a one-stop achievement of potato digging, soil-potato separating, stalks, weeds, and mulch films removing, potato conveying, grading, collecting, and bagging procedures. The tuber size grading can be adjusted according to the user's requirements. The potato harvesting operation requires only one tractor driver and two auxiliary workers, which effectively decreases the labor cost, simplifies the commodity potato processing links, and enhances the production efficiency. When the harvester is matched with a John Deal JDT654 type tractor with the rated power of 48 kW, its working productivity achieves 0.46 hm2/h. Meanwhile, the potato loss rate, injury rate, skin-broken rate, and impurity rate are less than 0.8%, 1.8%, 2.9%, and 1.2%, respectively. These four indicators decrease significantly compared with the original machine, which meet the requirements of the national agricultural industrial standard as NY/T 1130-2006 potato harvesting machinery. The whole structure is more compact, and beautiful, and the assembling unit mobility is better. It is suitable for harvesting the potatoes planted in the dry land and the film covering dry land with soft soil and no hardening.