The utility model discloses a semitrailer bearing plate supporting device. Characterized in that it is characterized in that it comprises, vehicle hopper, the vehicle hopper comprises a bearing plate.Wherein a support is arranged below the bearing plate, the bearing plate is fixedly connected with the support, the support comprises a cross beam and a longitudinal beam, protection plates are hinged to the two sides of the bearing plate, a supporting assembly is arranged between the cross beam and the longitudinal beam, a lower pressing plate is arranged on the supporting assembly, a limiting groove is formed in the protection plate, and the lower pressing plate is connected with the limiting groove in a sliding mode. When the semitrailer is used for loading some sharp cargos, the cargos cannot be scraped; goods such as stones, sand and the like are directly poured into the car hopper 1, and due to violent loading, the bearing plate 4 in the car hopper 1 is collided and extruded by thegoods, so that the bearing plate 4 is easy to smash and deform, pits are formed one by one, the attractiveness of a car is influenced, the pits are difficult to repair, and the service life of the carhopper is shortened.