The study of the dynamic behavior of underground structures, such as transportation tunnels, pipe lines, or … etc. to dynamic loads like moving loads, blasting, vibrations, or seismic loads is an engineering problem of dynamic soil-structure interaction. Numerical models for soiltunnel have been considered as an important design tools for many years. The accuracy of the results obtained depends on the knowledge of the input data for the tunnel and the surrounding soil. One of the most important problems in numerical modeling of dynamic problems related to input data is how you can simulate the effect of damping in soil-tunnel model. So, it is therefore clear that unless some techniques for simulation of damping effect are provided, shortage results would be inevitably produced due to shortage in input data. The aim of this study is that how to simulate the damping effect on the soil-tunnel models to represent the real behavior of the models. This paper studies the effect of damping on the behavior of soil-tunnel models under dynamic loads in time domain by using the FEM. There are many types of damping coefficients are studied in this analysis. It can be concluded that damping should be taken into consideration to represent the real behavior of soil-tunnel models. For application of this study, Cairo Metro Tunnel- Line 2, was chosen.