Abstract: Consideration of the dynamic effects of parameter uncertainties of the site soil and structural models is a basic common requirement for various seismic codes of NPPs around in the world. The anti-seismic standards generally provide two methods to analyze such effects. The first method is to directly numerically cope with the calculated floor response spectrum（FRS） results by means of deterministic approaches, and the second method is to analyze the FRS result set on the basis of probability statistics, which establishes the sample space by applying the Monte Carlo method. The influence and contribution of certain parameters cannot be screened in both of the above two methods, which only reflect the overall impact of various parameter uncertainties. On the basis of the statistic theory, a comprehensive index about a set of uncertain parameters impact assessment is presented and recommended in this paper, based on the floor response spectra of NPP analysis results, mainly including the correlation coefficient, regression slope coefficient and Tornado. From different angles, such indicators can be used to analyze the impact and contribution on the FRS for various parameter uncertainties, which finally results in an important sensitivity parameter sort.