The invention provides a clamp used for steel rail quenching. The clamp comprises a base, a guide rail assembly and a rolling shaft assembly. The base is provided with a bottom plate and two opposite supporting plates which are distributed at intervals and arranged on the bottom plate. The supporting plates are provided with connecting holes. The guide rail assembly is arranged between the supporting plates. The guide rail assembly is provided with a guide rail which is the same as a steel rail in structure and clamping plates arranged at the two sides of the first end of the guide rail. The clamping plates are constructed to be matched with the guide rail, and the first ends of the clamping plates at the two sides stretch out of the guide rail to form a first space used for placing the steel rail. The rolling shaft assembly is provided with a shaft penetrating through the guide rail, and bearings which are arranged at the two ends of the shaft and matched with the connecting holes. By the adoption of the clamp, quenching operation is convenient, and quenching quality of the steel rail can be guaranteed.