In order to understand soil-structure dynamic interaction, tests were done about low frequency vibration exciting a large proportion of raft-foundation-steel frame in trough and on rigid foundation.Changing the stiffness of the superstructure, four contrast tests were conducted.By signal spectrum and time domain analysis, the frequency and dynamic responses of the steel frame were obtained, and it was found that the frequency and dynamic responses had something to do with the soil, which were mainly caused by the change of superstructure stiffness.The natural vibration frequency of structure reduced in trough compared with that on rigid foundation.As the superstructure stiffness increased, the reduction coefficient of frequency increased, which in the test was up to 21.63%.Also, the maximum shear force for columns, peak acceleration and displacement of each floor had obvious variation, and the reduction coefficient of acceleration could be up to 30%.