Evaluating quantitatively the performance of earthquake-damaged structures is significant for facilitating post-earthquake reconstruction. However, it is difficult to consider the effect of earthquake-induced damage on structure. In this paper, a new method to build earthquake-damaged structure model (EDSM) based on damaged cross section analysis (DSA) procedure is proposed. DSA can consider the effect of earthquake-induced damage on concrete and reinforcement, respectively, and determine the skeleton curve of damaged cross section. EDSM is constructed by replacing plastic hinges of structure after earthquake with trilinear skeleton curve computed by DSA. This method is realized on RC frame structure and verified by the comparison of response between undamaged structure under sequence ground motions and EDSM under the last ground motion. Subsequently, there is more prominent reduction on the vulnerability of slight limit state than higher limit states by comparing the fragility of undamaged structure and EDSM. It can be indicated that earthquake-induced damage has more significant effect on elastic properties of structure. The proposed method to establish EDSM can well represent the structure after earthquake and assess quantitatively residual performance of earthquake-damaged structure and provide a reference for reconstruction decisions.