Abstract: To understand the tunnels' damage mechanism and the law of the dynamic response in the portal section, this paper establishes a numerical model based on the actual tunnel with spaces and staggered space and had the calculation. The calculating results show that for two parallel tunnels with staggered space, the relative displacement, maximum Mises stress and the amplitude of acceleration in the tunnel liner cross-section of portal section are affected by the vibration direction of seismic load. The dynamic responses of portal section still have significant differences between the left and the right tunnels even in the same vibration direction; however, the dynamic responses of the tunnel trunk section are close. When the seismic load is acted on one direction or the other combination direction, acceleration vector in any direction of space will exist simuhaneously on the lining, and the lining acceleration amplitude on the tunnel entrance is magnified.