Abstract: In combination with the construction process of Baoshiyan tunnel in Dazhou-Chengdu High-speed Railway, by using the finite-difference software FLAC~ 3D the characteristics of tunnel with karst cave beside are simulated and the numerical analysis concerning the influence of different dimensions and different distances of karst cave on the surrounding rock deformation is carried out. The results indicate that after the tunnel is excavated, the surrounding rock is convergented toward the karst cave and the tunnel. The surrounding rock between the karst cave and the tunnel is convergented in opposite direction, where is the most dangerous zone. The displacement of surrounding rock of hance, side wal1 and vault near the karst cave is larger than the corresponding parts away from the karst cave. With increase of the distance between the karst cave and the tunnel, the displacements of the tunnel’s main characteristic positions decrease in varying degrees, and are closed to the displacement of no karst cave state, at last. The displacements of karst cave’s main characteristic positions decrease in varying degrees, and the values convergence to zero. With increase of the karst cave dimension, the displacements of the karst cave’s and the tunnel’s main characteristic positions increase in varying degrees.