The transient behavior of the unsteady flow is very important for structure design of new type of high-speed trains. Different turbulent models and motion realization methods were investigated thoroughly for the simulation of unsteady flow around the trains passing by each other. Two-dimensional and three-dimensional models were simulated. The large eddy simulation (LES) for two-dimensional case indicates that LES can give better results, however the computational cost is too expensive for three-dimensional model. For the simulation of three-dimensional train pass-by event, sliding mesh method is more adaptive and robust than dynamic mesh method. The simulation results of the three-dimensional CRH3 model were compared with experimental data. The results show that the numerical method based on RANS equation with k – ε model and sliding mesh method provides a good tool for high-speed train design.