Guanshui Road Station of Guiyang Traffic Rail Line No. 2 Metro Station is located in the old city of Guiyang with a large population, complex traffic and dense buildings. The surrounding rock of the tunnel is of the grade of v and belongs to the super section tunnel. In order to reduce the formation disturbance caused by tunnel excavation this paper simulates the excavation with double-side-drift method by numerical calculation. The influence of core soil of different widths on the stability of tunnel excavation is analyzed. The displacement and mechanical characteristics of surface, vault, side wall and arch bottom are analyzed synthetically. It is concluded that the optimal core soil width is 10 308mm and it is suggested that monitoring and reinforcement measures should be strengthened during the excavation of core soil.