Abstract: In recent years，earthquakes treatmently occur，the new seismic code has been developed，the seismic analysis and identification of reinforcement were needed for the existing gyms built before the promulgation of new seismic code． Meanwhile，the gyms have gradually become an important place of refuge due to their large space and a number of people can be accommodated，therefore，carrying out dynamic analysis and seismic reinforcement research on the existing gyms has a great significance to the building which may become a seismic regional emergency shelter． In the assessment process after the Wenchuan earthquake，some problems occurred in existing steel building designs，such as poor seismic performance，large tilt of the steel columns，serious corrosion of the structure corrosion etc． The column-and-braces impaction on the entire structure was researched by the time history analysis of an existing typical steel gymnasium，that is Pengshan Gym，before and after reinforcement of the structure，the importance of lateral support in large span steel structure gyms was demonstrated． Then a simple and effective ways to seismic reinforcement of the existing gyms are pointed out．