Based　on　the　assumption　of　elastic　half-space　a　2D　lumped　parameters　model　was　used　to　simplify　soil　foundation.　An　analysis　model　of　soil-structure　interaction　was　constructed　based　on　the　soil　physical　model　for　mainly　studying　the　interaction　between　subsoil　and　superstructure.　The　seismic　responses　of　both　a　5-floors　building　and　a　15-floors　building　were　analyzed.　The　results　obtained　from　the　2D　lumped　parameters　model　of　both　medium　hard　site　and　medium　soft　site　were　compared　with　those　derived　from　the　rigid　foundation　model,　some　valuable　conclusions　were　obtained.