The invention provides a loss-reduction and loss-prevention elastic control soil-pressing mechanism for a potato harvester. The loss-reduction and loss-prevention elastic control soil-pressing mechanism is characterized by comprising a frame, a floating device, a soil pressing device and a power device, wherein the frame comprises vertical columns, reinforcing rods, vertical plates, transverse rods, connecting rods and lugs I; the floating device comprises supporting arms, a cross rod III, adjusting screw rods, lugs II, spring seat plates and compression springs; one ends of two straight-rod-shaped supporting arms are fixedly arranged at two ends of the cross rod III respectively; two supporting arms are parallel to each other; the soil pressing device comprises mounting plates, a coupler,a soil pressing roller and shields; two mounting plates are fixedly arranged at the positions, close to the lugs II, of the supporting arms of the floating device; a hydraulic motor is mounted at theouter side of one mounting plate with the inner side equipped with five shields; and the power output shaft of the hydraulic motor penetrates through the extending ends of the mounting plates and isconnected with the other end, far away from the soil pressing roller, of the coupler. The loss-reduction and loss-prevention elastic control soil-pressing mechanism provided by the invention has the advantages of loss reduction, loss prevention, good elastic soil-pressing effect, accurate and reliable adjustment, guarantee of a potato exposure rate, and improvement of the harvesting quality.