Abstract: Based on the characteristics of steel frames, a new model, named as simplified column-beam model, is developed for the seismic response of planar steel frames, planar double systems and spacial steel frame structures. The model takes into account the strength and the stiffness ratio of the beam-to-column, the deformation of joint panel, additional axial force, plastic hinge in the middle of the beam, material nonlinearity and geometric nonlinearity and the incongruity of intersection angle between planar double systems. It simplifies the analysis of highrise planar steel frames, planar double systems and spacial structures effectively. It is also applicable to the second-order elastic-plastic dynamic analysis of steel frames.