Abstract: The application of artificial boundary is a key issue in seismic analysis of the interaction system. The method that how to implement the viscous elastic boundary in SAP2000 was introduced and a framework module was set up and cycle variation of a series of different site soil considering soilstructure interaction was calculated. Besides， based on the design response spectra， total seismic force and maximum displacements of the upper structure were calculated， when considering the interaction or not. When the interaction was considered， especially the soft soil， the cycle of upper part， seismic force， maximum displacement of toplevel changed greatly.

Key words: soilstructure interaction, SAP2000, response spectrum, viscous elastic boundary, natural period