This article studies the impact of soil thickness and soil conditions on the peak ground acceleration and response spectrum of ground motion of step bedrock site by using two-dimensional seismic response analysis program of explicit finite element method.The distribution characteristics of ground motions are summarized.The SH wave is taken from recorded seismic waves of different frequency spectra.Research results are shown as follows:For the step bedrock field

the change of soil layer thickness has a more significant impact on the surface seismic response of the corresponding region and the surface seismic response of soil layer thickness constant region is not obvious.The soil conditions have an important impact on both PGA and response spectra.The peak acceleration of ground surface in soft soil and composite soil layer is greater than that of hard soil.The peak value of the response spectrum in soft soil site is greater than that of the response spectrum in the hard soil site

The peak response spectra period in hard soil is shorter

the peak response spectra period in soft soil is longer.The effect of soil properties on the response spectrum of ground motion is mainly reflected in the short period.