Abstract: Taking a real sixstorey twospan frame building for exemple, the soilframe structure system is simplied as twodimensional question, Soils are regarded as viscoelastic material, and frame structure is regarded as a nonelastic plane struture of bar system being composed of variable stiffness beam elements. The shock absorbing characteristics of tuned mass damper (TMD) and the effect of the soilstructure interaction(SSI) on the shock absorbing efficiency(SAE) are discussed in detail. In the condition of midsoft to midhard ground the effect of SSI can obviously reduce the storey displacement in range of 10% to 50% for multistorey framed building during earthquake. The SAE of TMD is best only when the vibration period of TMD is equation to the basic periods of (soils and) structure system being control, if not, the SAE of TMD will be reduced in range of 5% to 10%. On the soft ground condition the SAE of TMD almost lost due to SSI effects. It can be not necessary in some condition that TMD is adopted in structure designed by the assumption of rigid ground if the SSI effects are considered in the seismic design.