Most of steel beams in midspan bottom slab are fixed up following the shape of girder bottom edge with both ends anchoring to the bottom slab wedge. Due to the girder of long-span continuous rigid-frame bridge has variable cross section, the shape of steel beams in midspan bottom slab presents a curve opening downward, which does harm to the girder. Arranging steel beams along straight line in the bottom slab with both ends anchoring to the top wedge is better for girder to carry load. The analysis results of two methods analyzed by FEM shows that arranging of straight line lowers the stress of the top edge of girder meanwhile it increases the stress of bottom slab edge. Besides, the method lowers pressure stress and shear stress of the height middle of the girder where the steel beam anchoring and increases the main tension stress reservation which is good for the girder to carry load.