In order to study the mechanical properties of assembled T-typed steel vierendeel sandwich composite floors, the theoretical calculation formula has thus been deduced, followed by the establishment of the finite element model of assembled T-typed steel vierendeel sandwich composite floors with four simple supports by using ABAQUS finite element analysis software, with a tentative inquiry into the change of each influencing factor on the flexural bearing capacity of the composite floors. The results show that a change of steel plate thickness and steel strength has a significant impact on the flexural capacity of composite floors, while the increase of thickness of upper pouring concrete slab, the increase of concrete strength and the decrease of stud spacing between the upper concrete slab and lower steel structure have a certain impact on the flexural capacity of composite floors. The results of theoretical calculation show that it is feasible to distribute the overall bending movement of the composite floor section according to the rigidity of the upper and lower rib sections, with a design and calculation of the composite members and tension bending members respectively.