Combined box girder widening structure suitable for widening old bridge

The utility model relates to a combined box girder widening structure suitable for widening old bridges, which comprises a prefabricated bridge deck slab, a channel steel box, widening seams and a pavement structure layer, the prefabricated bridge deck slab is connected above the channel steel box, the pavement structure layer is positioned above the prefabricated bridge deck slab, and the widening seams are connected with the channel steel box. The prefabricated bridge deck is connected with a bridge deck of an old bridge through a splicing-widening seam, and the pavement structure layer is connected with a pavement structure layer of the old bridge. Compared with the prior art, a cast-in-place process is replaced by a prefabricating and splicing construction process, so that the construction speed is increased, the interference to the surrounding environment is reduced, the widening construction quality is improved, the widening structure is more convenient to install and construct, the construction cost is