In order to study the influence of different excavation methods on the deformation of surrounding rock at the entrance of a super large cross-section mountain tunnel, a numerical model was established using ABAQUS finite element software based on the Hangou No. 2 Tunnel in the Yanshan Area. The horizontal convergence, arch settlement, bottom arch, and surface settlement of the surrounding rock were analyzed when the right tunnel was excavated with a leading small guide tunnel and the left tunnel was excavated with three steps and seven steps, respectively. The distribution of plastic zone and the influence of lining support stress. The results indicate that the deformation of the surrounding rock is relatively small during the excavation process of the small pilot tunnel. The deformation law of the surrounding rock of the right small pilot tunnel is basically the same when expanding from the inside to the outside of the tunnel and from the outside to the inside of the tunnel. The former has advantages for the construction of the mountain tunnel entrance section. After the left and right tunnels are connected, the maximum horizontal convergence, arch settlement, bottom arch, surface settlement, and maximum principal stress of the lining of the right tunnel are 1.35 mm, 3.91 mm, 2.88 mm, 3.39 mm, and 0.11 MPa, respectively. The left tunnel is 1.52 mm, 5.57 mm, 2.67 mm, 5.34 mm, and 0.35 MPa, respectively. The advanced small pilot tunnel excavation method is more conducive to controlling the deformation of the surrounding rock, while the plastic strain of the surrounding rock and surface settlement are greater under the excavation of the three step tunnel. The research results can provide a certain theoretical basis and guidance for similar projects, and achieve safe and efficient excavation operations for large cross-section mountain tunnels.