Abstract: In this paper,a stochastic seismic response analysis for a nuclear power plant structure is carried out considering SSI effect,in order to discuss the influences of the uncertainty of soil on the nuclear power plant structural seismic responses. The soil-structure dynamic interaction is modeled by setting the spring and damping elements on the boundary using the finite element analytical program ANSYS. The un-certainty of the dynamical parameter of soil can be achieved by adjusting the values of these parameters re-lated to the aforementioned elements. Finally,a reactor building in a 1000MW class pressurized water reactor nuclear station is numerically analyzed. The comparison of the numerical results of stochastic method with those of deterministic analyses indicates that this method is practical,and it is a useful balance for the deter-ministic analytical approach. The combination of these two methods can yield much more reasonable results for evaluating the effects of the property uncertainties of soil on the seismic responses. The conclusions pro-vide some references for the evaluation of the sensitivity of seismic nuclear power plant structural response to uncertain parameters.