The 3D nonlinear FEM models of concrete-filled square tubular column with internal diaphragms and steel beams with reduced beam section bolt-weld joints, involving geometric, materials and contact nonlinear were founded. The results of FEM are agreed to that of tests, so we can conclude that FEM in this paper is correct. Then the bearing capacity behavior of joints under cyclic loading are analyzed, including P-Δ skeleton curves, P-Δ hysteretic curves, the dissipating energy ability and destruction form. The analysis results show that the plastic hinge in the joint with reduced beam section is removed to the reduced beam region. The joints that studied in this paper present excellent ductility and dissipating energy ability, therefore, all of them have a good seismic behavior.