Abstract: Considering the characteristics of dynamic interactions between soil and tunnel and a train system, a 3D dimensional finite element model for a tunnel-train system considering seismic loads was established, and the explicit parallel method based on contact balance bisection algorithm was used to solve the problem. The seismic dynamic response of a tunnel-train system was researched, and the running safety of the train was evaluated based on the numerical analysis. The influence of the train-speed and the earthquake intensity on running safety were analyzed. The numerical analysis results show that the effects of seismic loads on the dynamic responses of the tunnel-train system are significant, and the dynamic responses of the system subjected to an earthquake are greatly increased. The running safety and the running smoothness are greatly decreased. The dynamic train loads barely infect the dynamic response of a tunnel structure. The running safety indicators are not sensitive to the change of train-speed without an earthquake. However, during earthquake, the impact of the train-speed on the running safety increases with the increasing intensity of an earthquake.