For the famous benchmark model of jointed beam proposed by the Sandia workshop on the modeling and simulation of structures with jointed interfaces, a symmetricmodalmodel and an antisymmetricmodalmodel were developed by the flexible support method in a relative description style separately. Then the modes were analyzed and the flexible parameters of the support were identified from the experimental data. A FEA was also carried out, in which the joint was modeled as a virtual material with identified parameters. The modes of the joined beam predicted by the analytical method and FEM are well coincident with the experimental results.