Abstract: In order to solve existing problems of performance index and seismic design of main buildings for thermal power plants, experimental study on the seismic performance was conducted, and displacement-based seismic design (DBSD) method was proposed.Damaged pattern and deformation performance index under different intensities earthquake effect were given through the experiment study, seismic performance objectives were confirmed at the same time.Performance levels were quantified with storey drift ratios.Application key points and procedure of the DBSD method were determined for main building design.It was used to calculate one main building in different performance levels.The results show that the DBSD method can effectively ensure safety of the structure and equipment in different earthquake action, especially structural damage control under the strong earthquakes.The design index given in the paper can meet the demands, which can provide reference and application for similar engineering design．