The evolution of plastic deformation and damage in steel frame buildings caused by seismic action is simulated based on a modified damage model. This model combines nonlinear isotropic and kinematic hardening criteria with a damage evolution law expressed in terms of plastic displacement. A nine-story steel frame is chosen as a reference structure, and a nonlinear damage analysis is performed using ABAQUS with the El Centro earthquake accelerogram as input. The results reveal that the beam ends on the upper floors exhibit more obvious plastic deformation and form damage domains, which is consistent with the observed seismic damage of high-rise steel structures during the Northridge earthquake.