The utility model discloses a prestressed stretching steel beam, and belongs to the field of architectural engineering. The prestressed stretching steel beam comprises a main steel beam body, wherein the main steel beam body comprises a top plate, a bottom plate, first, second, third and fourth transverse baffles, first and second pressure bearing steel plates, a clad steel plate and web plates, and the first and second pressure bearing steel plates are arranged in parallel; the top plate, the first, second, third and fourth transverse baffles are sequentially arranged between the first and second pressure bearing steel plates in parallel from top to bottom, and corresponding rectangular steel bar perforating grooves are formed in the middle sections of the central lines of the first and second pressure bearing steel plates in the length direction; the web plates are welded in each layer of cavity between the top plate, the first, second, third and fourth transverse baffles, and the bottom plate. The prestressed stretching steel beam provided by the utility model has the advantages of simple structure, low cost, lighter weight and convenience in construction, is suitable for long-span bridge construction, and can effectively reduce the risk of breaking of a box girder.