Abstract: The generation algorithm of the artificial ground motion is analyzed,the dynamic analysis model and method for the nuclear power plant seismic behavior under soil-structure interaction are explored,and the effect of variations of both the soil property and the load on the building responses is studied via comparison of the floor response spectra.The results show that compared with the load,the soil property con-tributes more to the seismic behavior of nuclear power plants,and that the difference of seismic behavior arising from the parameter variations can not be fully enveloped by the broadened floor response spectra cal-culated with one specific soil property.Therefore,it is necessary to envelop the floor response spectra with various soil properties.