The objective of this study is to establish a simple soil-structure-interaction analysis system in time domain with frequency-dependent soil springs. This paper presents formulation of equations employed in the analysis system. In the system, the non-linear analysis is performed for each iteration step in the time domain using the soil springs with linear approximation, while frequency-dependence of soil springs is evaluated in the frequency domain as pseudo-forces which are recalculated in each iteration step. A response of a building with embedment is investigated using the proposed system.