A lower side bearing for a wheel truck, including: a first friction board, a second friction board, an inner pedestal, a bearing sleeve sleeving the inner pedestal, a pressure block, a pressure plate, and an elastic component. The pressure block is disposed on an upper part of the inner pedestal, and the second friction board is disposed on a top of the pressure block. The pressure plate is disposed on an upper part of the bearing sleeve, and the first friction board is disposed on a top of the pressure plate. A friction coefficient μk of the first friction board and a friction coefficient μz of the second friction board meet the relation: μk>μz. The elastic component is disposed between the inner pedestal and the bearing sleeve for controlling a relative position of the inner pedestal and the bearing sleeve.