Railway route selection design in the plateau mountain area is a complicated work, with high construction difficulty, many influencing factors, and strong comprehensiveness. The terrain of the Sichuan-Tibet railway is complicated and the construction conditions are difficult. Therefore, the systematic and reasonable route selection design can help the construction of the Sichuan-Tibet Railway to the greatest extent. This paper selects the Gyaca County-Nang County section of the Sichuan-Tibet Railway. Based on the analysis of regional CAD topographic map and three-dimensional map, combined with multi-source remote sensing and other geological exploration analysis, the topographic and geomorphological features of the selected area can be obtained, the principles of the selecting line in the plateau mountain design area can be formulated, which can provide a theoretical basis and implementation reference for the optimization decision of the route selection scheme of the plateau and mountain railway in the future.