Seismic response analysis of highrise isolated structure was under rare earthquake carried out using timehistory method. Plastic deformation, story displacement and story acceleration were all included. The results show that plastic deformation has not highly developed and the structure can be used after simple repairation. Plastic hinges appear all at the end of frame beams, and no one is found at the end of frame columns. Story displacement is centralized at isolation layer, and story drift is small on superstructure. Story acceleration is reduced significantly.