The long-term cyclic effect of aerodynamic pressure acting on tunnel wall is the important trigger of secondary lining detached from a high-speed railway tunnel wall. To investigate the influences of high-speed train's speed on the basic characteristics of aerodynamic pressures, a three-dimensional numerical simulation was conducted to study the aerodynamic pressure at typical position of tunnel (near tunnel entrance, middle tunnel, near tunnel exit). The results show that the passing of train head makes the difference of aerodynamic pressure acting on monitoring cross section enhance, which showing obvious three-dimensional characteristics. The three-dimensional characteristics of aerodynamic pressure near tunnel entrance are mainly affected by the volume of compressed air and distance between monitoring cross section and tunnel entrance. The characteristics weaken with increasing distance, and gradually transform to one-dimensional. After train head enters the tunnel entrance, and before tail leaves exit, the positive peak value of aerodynamic pressure at different monitoring points of tunnel body are mainly affected by the compression wave induced by train head entering into tunnel entrance. The negative peak value and peak-to-peak value of aerodynamic pressure acting on the tunnel wall in the middle of tunnel's longitudinal axis are greater than that near the tunnel entrance and exit. After train tail leaves the tunnel exit, the negative peak value near the tunnel entrance is greater than that near the tunnel exit, and the positive peak value is smaller than that. The three-dimensional characteristics of aerodynamic pressure near the tunnel exit is similar to that near the tunnel entrance. However, the effects of the train speed and distance on three-dimensional characteristics of aerodynamic pressure are more complicated.