Abstract: 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 IS-floors building were analyzed. The results obtained from the 2D lumped parameters model of both medium hard site and medium soft site were some valuable conclusions were obtained. compared with those derived from the rigid foundation model.