Corns are cleaned and are delivered to a grain storage section of a corn dryer by a hoister, grain feeding is controlled automatically by a material level detector, the operation direction of the corns in the dryer and flow direction of hot wind form concurrent, so processes of preheating, drying, tempering and drying are achieved, the operation direction of the corns in the dryer and flow direction of cold wind form counter flow to achieve a cooling process, thereby achieving ideal drying effect, and the corns are sent out by a grain discharge machine finally.