To avoid rock falls and distortion of support structure occurring in the construction of tunnels in high stress field, the designers had plans to use either stage excavation or pilot heading excavation method for the tunnel. Full face excavation method, pilot heading excavation method and stage excavation method were simulated by the finite difference software FLAC3D. After analyzing and comparing the features of the distribution of the deformation field, plasticized deformation field and stress field, the stage excavation method was proposed for the tunnel based on the data produced. After adopting the said method, the stability of the excavation face was improved dramatically and the data collected at the site coincide well with the numerical simulation results.