To ensure that the steel tube and core concrete work together for large section rectangular concrete filled tube columns, the allocated beams are installed where the node area of concrete filled tube columns floor. As force transmission components, allocated beams make the external load beared by the steel tube and core concrete together, and the deformation of the steel tube and core concrete basically meets the plane section assumption. The design of allocated beam can apply the finite element method and elastic foundation beam method advanced by this paper. Finally, the comparative analysis between analytical and numerical solutions of single allocated beam, verifys further the rationality of theory.