In earthquake engineering, the conventional wave motion analyses usually took the subsoil as only one layered soil, and treated the subsoil by using a single freedom system model. Moreover, these methods were often adopted in time domain. In fact, the subsoil are usually stratified due to its forming in different ages, so there exist multiple interfaces which leads to multiple repeated tracings of reflecting and refracting waves in time domain analysis. To avoid the difficulties, a frequency domain analysis method is carried out for linear soil system in this paper, which allows combining all the upward waves and downward waves to a single upward wave and a single downward wave, respectively, and therefore raises great efficiency. The stochastic response analysis of the displacement of layered soils is then performed. The result indicates that, there exists the essential difference in power spectral density (PSD) between stratified soils and single-layer soil, the former has multiple peak values, while the later has only one peak value, and stratified soils have strong filtering effect in high frequency ranges, which can be considered as a low-pass filter.