The invention belongs to the technical field of fabricated steel structures of civil engineering and discloses a floor structure with gridding beams and composite boards. Columns are arranged at the four corners of the periphery of each floor unit, main beams are arranged at the four edges of the periphery of each floor unit, and connecting joints of the main beams and the columns are in rigid connection; the gridding secondary beams are arranged on the inner sides of the periphery of each floor unit, and the gridding secondary beams and the main beams are hinged; connecting joints between thegridding secondary beams are rigid joints, a plurality of grid units are formed between the gridding secondary beams, and each composite board used for pouring concrete is arranged on the corresponding grid unit; and based on the composite boards, each floor unit is poured into a concrete floor. A construction method is simplified, the construction speed is further increased, wet operation of a construction site is reduced, thus the purposes of energy conservation and environmental protection are achieved, and intelligent development is accelerated.