The modal experiment of the three-section crossbeam was carried out by single-input multi-output method. Identify the stiffness and damping with single-degree-of-freedom identification method. Use ANSYS software APDL programming language and experimental data to establish the finite element model of joint surface of three-section crossbeam. Use modal analysis method analysis the three-section crossbeam which establishes FEM modeling of joint surface. The comparison of the analysis result and experimental result are shown. The FEM result of the three-section crossbeam established FEM modeling of joint surface is basically tally with the experimental result, the modeling methods for joint surface is feasible.