Abstract: Based on accelerograms on rock site from the Wenchuan earthquake, analyses of peak ground motion parameters and standard response spectra for nuclear power plant are made. The authors paid attention to the fact that the ratio (PGA/PGV) could be affected by PGA and epicenter distance, which is taken into account in developing standard response spectrum. This paper verified that such affection would significantly influence the shape of the deduced standard response spectrum. It is also validated that the vertical PGA on rock site may be much greater than 2/3 of the horizontal PGA. Compared to the pseudo-velocity spectra, the standard spectra are smaller in the long period region. Two new methods are presented to fit the mean-plus-one-standard-deviation spectra more aptly than conventional method.