Abstract: The relation between AP1000 certified seismic design response spectra （CSDRS） and the response spectra defined by different regulations were analyzed, and it indicated that it was necessary to compare the site specific response spectra (SRS) with AP1000 CSDRS on the same ground level. The corresponding CSDRS at two levels of design rock and foundation base were calculated by inversion method for the five AP1000 design site models. The analysis results show that the calculated CSDRS at two levels of design rock and foundation base could not envelop the design response spectra anchored at the peak ground acceleration of 0.2 g, which is used in the seismic design of nuclear island of existing nuclear power plant as specified in RG1.60. Therefore, it is suggested that if the AP1000 nuclear power plant is not built on the hard rock site, the conservative analysis of the AP1000 CSDRS should be carried out.