Abstract: According to statistical analyses and shaking table tests of seismic damage of RC frames, the performance levels and corresponding damage degrees based on inter-story drift subjected to earthquakes were proposed. Seismic vulnerability analysis was adopted to analyze existing RC frame structures built in different historic periods to obtain the vulnerability curves and their matrixes. In order to evaluate the damage degree subjected to the expected earthquake in future, the seismic damage index method was also put forward. Finally, taking an exhibition hall as an example, the seismic performances of the structure before and after seismic strengthening were evaluated, and the effect of seismic reinforcement was verified.