Numerical modeling of a soilstructure interaction （SSI） system model is performed by Program SASSI2000 in this paper. The shaking table test and the analytical methods are briefly reviewed in this paper. The seismic responses of superstructure overlying two types of ground are calculated by Program 2000

associated with real combinations of three seismic events

three input peak acceleration levels and two input directions. Comparisons between the test and calculatation results indicate that the analysis model is able to simulate the performance of SSI system under seismic excitation

and the calculated results are in fairly agreement with the test results.However

it shows that the seismic responses of superstructure on soft soil under strong ground motions are different from that of tests to some extents in that the finite field region in a flexible container in the tests is replaced by the semiinfinite horizontal layers in the analysis. Both the test and numerical results obviously show that SSI effects have an important influence on the seismic responses of superstructure.