The invention discloses a connecting structure of a prefabricated regenerated block concrete slab and a superposed beam. The connecting structure comprises a left side plate, a right side plate and the superposed beam. Outwards stretching racks erected on the upper surface of the superposed beam are arranged at the ends of the left side plate and the right side plate, and thin steel plates erectedon the upper surface of the superposed beam are pre-buried at the edges of the plate bottoms of the left side plate and the right side plate; and an outwards stretching plate rib perpendicular to theaxial direction of the beam and a plate rib parallel to the axial direction of the beam are arranged on each of the left side plate and the right side plate, the outwards stretching plate ribs of theleft side plate and the right side plate are mutually lapped, and a beam longitudinal bar and a beam stirrup of the superposed beam are mutually strapped. The invention further discloses a construction method of the connecting structure. According to the connecting structure of the prefabricated regenerated block concrete slab and the superposed beam, the construction load is borne by arranging the outwards stretching racks at the ends of the left side plate and the right side plate, the problem that construction is complex due to the fact that a large number of vertical supports needs to beerected mostly in the current floor slab assembling process is solved, the pre-buried thin steel plates can serve as soffit formworks of post-poured concrete, the site formwork supporting workload isdecreased, the construction efficiency is improved, and the connecting structure meets the building industrialization requirements.