Abstract: Based on elastic-plastic time-history analysis of the MSCSS without additional dampers under seismic action，it was given that different arranging schemes of the additional dampers from different angles． The Hilbert- Huang transform method ( HHT) was used to obtain the progressive power spectrum of measured seismic wave，the non-stationary trigonometric series method was used to obtain a plurality of artificial waves，and multiple artificial waves with similar response spectrum were selected as the sample library of a random process，the reliability analysis method based on the probability density evolution equation was used to MSCSS under different arranging schemes of additional dampers，which was compared with the mega frame structure． Ｒesearch shows that reliability of MSCSS is much better than mega frame structure，arranging schemes of the additional dampers have great impact on reliability of the MSCSS，the performance of MSCSS is the best when additional dampers are arranged in the maximum story drift layer and the maximum displacement layer of sub-structure respectively．