The inner contour mode of ballast track railway tunnels with speed less than 160 km/h in China nowadays can not meet the requirement of large maintenance machinery. The main influencing factors of inner contour of electric railway tunnel and singleline/doubleline tunnel, such as building boundary, hanging mode and layout of overhead catenary system, space requirement of large maintenance machinery and setting of ditch and cable trench, etc. are comprehensively analyzed. The control size of inner contour of singleline/doubleline ballast track railway tunnel is decided; and the inner contour mode is selected. The comparison between two inner contour modes is made in terms of structural safety, economical benefits and construction efficiency. The study results can provide reference for the selection of inner contour mode of ballast track railway tunnels in the future.