Abstract: A new type of floor slab applied to prefabricated steel structures was proposed in the paper. The lower floor is the structural floor and the upper floor is the building floor. The building floor is poured at the decoration stage, and the structural floor and beam are integrally manufactured in the factory. The beams are all hidden in the floor. The position of the partition wall does not have to correspond to the beam, which makes the layout of the partition wall flexible and meets the individual requirements of owner for functional layout. Web openings allows the pipeline in the floor to easily pass through the beam, which is conducive to the personalized layout and installation of the pipeline during the decoration stage, and at the same time facilitates later maintenance and renovation. In order to study the mechanical properties of this floor during construction, static performance tests were performed on two beams and floors during construction. The cracking load, crack development distribution, design load and failure mode of two floors were analyzed. The design bearing capacity of the beam was analyzed, and the results obtained from the finite element analysis were compared with the test results. The results showed that the invisible beams and floors had reasonable bearing capacity during the construction stage and could meet the requirements of construction bearing capacity. Based on the test results, a calculation method for the bending bearing capacity of the invisible beams and floors was proposed.