The different surface dig angle is one of the reasons for the biased tunnel. Due to the surface asymmetry, the force on the two sides of the tunnel is different from each other, leading to damage to the lining of the tunnel. The finite element analysis was used to study different surface dig angles, the deformation process around the tunnel and the distribution characteristics of tunnel bolts and the plastic zone. When the surface dig angle is greater than 30°, the tunnel is clearly affected by biased pressures and the plastic zone on the deeper side is enlarged, which can provide some theoretical basis and construction suggestions for the tunnel design under the topographic biased pressure.