Abstract:After Wenchuan earthquake, many buildings presented varied degrees of destruction in Sichuan and Chongqing province. The large scale damaged buildings need security identification to ensure the safety of the extant buildings and resettle the victims as soon as possible. In view of this, a fast and feasible method frequency method for building identification was introduced in this essay. To some extent the decrease of the frequency reflects the earthquake damage degree to the structure. Through the analysis of dynamic performance parameters (natural vibration frequency, damping ration) of the structure and compare with similar structures, the relationship between the structure rigidity degradation degree and the earthquake damage degree to the structure can be reached, which determined the gradation of earthquake damage. Using this method, nearly one hundred buildings (masonry structure, frame structure, masonry building supported by RC frame) were detected. Results showed that the method was simple and feasible,and was able to determine the earthquake damage degree to the structure accurately.In the last,a simple statistical analysis about seismic damage of the builds detected has been made.The data accumulated would be valuable for damaged building renovation and increase new building’s seismic performance.