Abstract: The interactions within the components of L-section concrete-filled steel tube (CFT) with binding bars subjected to axial load are analyzed. By reasonably setting the effective confined areas of L-section CFT with binding bars, the L-section is divided into a square and two rectangular sections. The rectangular sections have binding bars while the square section has no one. The logical assumptions on the characters and boundary conditions of the cutting section are suggested. The constitutive relationship of confined concrete is adopted to build the equivalent constitutive relationship of the core concrete confined by L-section steel tube with binding bars and the parameters are confirmed through experimental data. The experimental specimens are calculated by the proposed constitutive relationship. The calculating results of load-strain curves are in good agreement with the experimental ones.