The medium-size potato harvester is equipped with a three-point suspension system, which can be easily connected to a tractor and towed through the field. It is capable of working two rows at a time and covering two ridges in the field at a time, harvesting the crop quickly and easily with minimal labor and cost. It can achieve adjustable row spacing and complete the digging, conveying separation and strip collection operations in one go. The main components include a width-limiting disc knife consisting of a disc knife, a fixing frame, a compression spring, and an adjustment device; a digging component consisting of a knife frame, a knife bar, a main shovel, an auxiliary shovel and a digging angle adjustment mechanism; a suppression depth-limiting device consisting of a contoured depth-limiting wheel, a bracket, and an adjustment mechanism; a grid-type conveying separation screen consisting of a toothed belt, steel bars, a driving wheel, a passive wheel and a shaking wheel, and a strip collecting device.