Abstract: The three methods for determining the influence intensity of the historical earthquake in nuclear power plant sites are the method for extrapolation of the seismic isosematics, the methods of judging data of earthquake damage investigation in ancient buildings, and the method of investigation and judgment of earthquake damage near the sites. Taking a nuclear power  plant site in Hebei Province as an example, the influence intensity of the 1679 Sanhe and Pinggu M8 earthquake on the site was judged by the method of historical earthquake and isoseismal inference, which was Ⅶ degree, the influence intensity of the site was assessed by the investigation data of ancient buildings damaged by Tangshan M7.8 earthquake in 1976 as VI degree, and the influence intensity of the site was assessed by household-to-household earthquake damage investigation as V degree.