Abstract: Although the pressure wave generated at a tunnel entrance is an infrasonic one with an intensity that is usually weaker than that of a micro-pressure wave, it may induce some new environmental problems if train speed is increased in the future. In this paper，a numerical simulation study is conducted regarding the properties of a pressure wave at a tunnel entrance that is generated by a high-speed train CRH3 running into the tunnel by using the finite volume method, the dynamic mesh technique of the arbitrary sliding interface(ASI) method, a PISO algorithm and a SST turbulence model with high Reynolds numbers. The results show that the pressure wave generated at a tunnel entrance is made up of negative and positive pressure pulses emitted from the train head and tail while the train is running into the tunnel, and it has the features of directional propagation and attenuation with an increase of distance. Furthermore, the amplitude of the entrance wave is inversely proportional to the observation distance and proportional to the cube of the train speed.