The invention provides a deformed reinforcing bar, a truss structure and a floor module structure. The deformed reinforcing bar comprises an accommodating recess so that when used with a strut member to construct the truss structure of the invention as a top or bottom chord, the bending regions of the strut member can be fitted into the accommodating recess of the deformed reinforcing bar to simplify the welding process to achieve consistent welding quality as well as enhance the strength of the truss structure after pouring concrete. Additional transverse ribs and concave marks can be added to the surface of the deformed reinforcing bar and the surface of the accommodating recess to enhance bonding capability with concrete. The floor module structure can be assembled with a plurality of truss structure.