The utility model discloses a steel-rail-positioning rail clamping device which comprises a backing plate, reinforcing plates, U-shaped channel steel, handles, threaded positioners and nuts, wherein the backing plate is placed on the bottom surfaces of concave cavities at two vertical ends of the U-shaped channel steel; the reinforcing plates are respectively clung to the inner side surfaces of the concave cavities at the two vertical ends of the U-shaped channel steel respectively; openings are respectively formed in four side surfaces of the end part of the U-shaped channel steel; the nuts are welded at the openings; each threaded positioner is matched with the corresponding nut; each handle is fixed at the end part of each threaded positioner. According to the utility model, the load is borne by fitting of the backing plate placed in the concave cavities at the two vertical ends of the U-shaped channel steel with the upper surface of each steel rail, and accurate and reliable positioning of each supporting leg in the height direction is determined; the handles are rotated to enable the threaded positioners to lock each steel rail, and stabilities in the horizontal direction and the vertical direction of each supporting leg are ensured.