Abstract: Based on the statistics of 350 sets of strong-motion acceleration records on bedrock in Next Generation Attenuation（NGA） database of the US and 14 sets of strong-motion acceleration records on bedrock in Wenchuan M_W7.9 earthquake and Lushan M_W6.6 earthquake, normalized horizontal spectral accelerations on bedrock for seismic margin assessments of nuclear power plants were suggested. The effects of earthquake magnitude on frequency contents of strong-motions were adequately taken into account in this suggested spectral acceleration, which could help evaluate the effects of different seismic tectonic environments on normalized spectral acceleration inputs in the seismic margin assessments of different nuclear power plants. In comparison to the normalized spectral accelerations suggested in RG1.60, this suggested spectral acceleration could reflect the high frequency contents of strong-motions induced by medium-strong earthquakes in near field more reliably.