Abstract: In order to obtain more accurate spectral accelerations for seismic design, 2661 strong-motion acceleration records in the Next Generation Attenuation (NGA) West2 database were statistically analyzed, the effects of earthquake parameters on the middle to long periods of the ground motion spectral accelerations were studied, and normalized horizontal spectral accelerations on bedrock (site classification I in the Chinese standard) and non-bedrock (site classification II and III in the Chinese standard) for seismic design were established. The results indicated that the spectral accelerations of the ground motion were significantly influenced by site conditions and earthquake moment magnitudes, meanwhile they were slightly influenced by distance parameters of the earthquake source. Comparing to the spectral accelerations for seismic design suggested in RG1.60 of USNRC and GB50267-97 in China, the spectral accelerations of the ground motion obtained in this paper could evaluate the effects of site surface geology characteristics and earthquake moment magnitudes on the middle to long periods of the ground motion more reliably. Finally, the spectral accelerations for seismic design considering the influences of site conditions and seismotectonic environments were established, which could be used as the ground motion inputs in the site selection and seismic design of nuclear power plants on non-bedrock sites.