This paper proposes that on the basis of near-source saturation characteristic of ground motion, the peak ground motion acceleration and the acceleration response spectra of diffuse earthquakes affecting the nuclear facility site can be determined by the statistic method. In view of the problem of insufficient statistic samples due to fewer qualified strong earthquake records on the bedrock site, it also proposes that according to the features of ground motion response of the soil, the acceleration records on the soil site can be transformed into the equivalent acceleration records on rock site for a simultaneous statistic analysis together with the records on rock site. Consequently, we have obtained by this method the near-source peak acceleration and the acceleration response spectra of small and moderate earthquakes on the site that could meet the need of nuclear facility and made a comparative analysis to the results from relevant researches. This new method for determining diffuse earthquakes is only preliminarily verified in the paper and further research is needed for practical application. This paper suggests that on the basis of near-source saturation characteristic of ground motion, the peak ground motion acceleration and the acceleration response spectra of diffuse earthquakes affecting the nuclear facility site can be determined by the statistic method. statistic samples due to less qualified strong earthquake records on the bedrock site, it also proposition that according to the features of ground motion response of the soil, the acceleration records on the soil site can be transformed into the equivalent acceleration records on rock site for a simultaneous, statistic analysis together with the records on rock site. consequence, we have obtained by this method the near-source peak acceleration and the acceleration response spectra of small and moderate earthquakes on the site that could meet the need of nuclear facility and made a comparative analysis to the results from relevant researches. This new method for determining diffus e earthquakes is only preliminarily verified in the paper and further research is needed for practical application.