Abstract: The dynamic soil-structure interaction(SSI)is one of the most important subjects in earthquake engineering.A time-domain finite element method(FEM)for analysis of two dimensional dynamic soil-structure interactions due to seismic excitations is presented.Emphasis is placed on how to simulate transient wave propagation in unbounded media and how to realize the earthquake input.In the proposed finite element procedure,both the method for earthquake input and the local transmitting artificial boundaries for finite analysis domain are established based on the cylindrical wave equation.The proposed method is simple and efficient,and the time-stepping scheme using Newmark's method in conjunction with the method is unconditionally stable,allowing for efficient and reliable time-domain computations.Numerical examples are presented to illustrate the validity and accuracy of the proposed method.