The utility model belongs to the technical field of a detection device for a rail surface and discloses a steel shift machine for the detection of the rail surface, which comprises a steel shift device, a horizontal movement mechanism, a fixed supporting frame, a transmission chain, a direction changing chain sprocket, a supporting chain sprocket, a trolley guide rail and a hydraulic station, wherein the steel shift device comprises a clamping device, a guide rod, a pin shaft, a trolley and a hydraulic cylinder with a linear sensor. The clamping device comprises a hydraulic cylinder, a pin shaft, a clamping device body, a gear rack, a gear, a clamp with tooth, a pressing cover, a pressing plate, a spring and a shaft; the horizontal movement mechanism comprises a shift hydraulic motor, a supporting seat, a bearing seat, an encoder, an encoder mounting seat, a connector, a transmission shaft and a chain sprocket. The steel shift machines form a straight line shape and are arranged outside a roller way of a production line. The clamping device of the steel shift machine is automatically controlled by hydraulic pressure, so the utility model is safe, lifts quickly steel rails, and ensures the production rhythm of the production line; the utility model has the advantages of simple structure, few components and parts, high reliability and less investment.