The invention relates to a prestressed composite beam structure, which comprises two mutually connected concrete beams, wherein a plurality of steel bar bent hooks are arranged inside the concrete beams; the end parts of the plurality of steel bar bent hooks are provided with screw threads and extend out of the end parts of the concrete beams; each of the two concrete beams is provided with a first steel plate screwed with the steel bar bent hooks on the end surface of connection points; a second steel plate is vertically and fixedly arranged on each of the first steel plates; the second steel plates of the two concrete beams are screwed into a whole; a prestress pipeline is arranged inside each concrete beam; a prestress steel stranded wire is arranged in the prestress pipeline in a penetrating way. The prestressed composite beam structure has the advantages that the structure is simple; the assembled construction of the building structure is realized; the construction efficiency is effectively improved; the construction period is shortened; safety and high efficiency are realized.