The generalized damage variable is defined based on a deformation equivalent principle. Stiffness damage of each level can be calculated by stiffness damage integration from material?level. This method can be used to evaluate the stiffness damage for material, section, member, story, and structure. The numerical simulation model of the“single span 12?story RC frame model test” was built by using the software ABAQUS. Multi?level stiffness damage evolution of this model was analyzed. The numerical results show that under El Centro seismic motion, Story 3?7 were damaged seriously with the beam?hinge failure mode;story 8 was damaged seriously with the column?hinge failure mode;the end sections of the columns and beams of story 3?8 were damaged seriously with concrete crushing. The accordance of the numerical and experimental results shows the multi?level stiffness damage evolution analysis can reflect the structural inhere damage mechanism.