Abstract: To the problem of the dynamic interactions between soil and buildings, a investigated lump model is established for studying the dynamic interaction between soil and buildings. Then a numerical approach by wave propagation simulation for the study is presented. It is a simple approach to study the earthquake responses of buildings located in city. The numerical results show that the existence of buildings causes the long coda wave phenomenon during seismic ground motion, and the vertical earthquake action has a strong influence on the horizontal earthquake responses of buildings.