Abstract: The stability of a tunnel is often affected greatly by its surrounding faults, and it is important to analyze the relevant mechanisms using numerical methods. Regarding the non-continuity of the rock mass, the geometric characteristics of real rock were simulated by means of a discontinuous network diagram using the GeoSMA-3D program. A three-dimensional tunnel model was set up in which the distribution character of the structural plane within the rock mass could be understood. Then, the numerical model was imported into a DDA program, which was applied to make a dynamic analysis and simulation of the destruction process of the tunnel. Meanwhile, the dip angle was altered and the failure process was simulated, and the results show that the stability of a tunnel is greatly affected by the dip angle of the faults.