Research Conclusions: The topography and geological conditions are very complicated in Southwestern China, so the full investigation of geological conditions along the line should be made so as to avoid complicated and seriously unfavorable geological section in course of route selection. The systematical introduction is given to several typical examples of route selection based on geological conditions on the primary survey stage for reconstruction of Guizhou-Guangxi Railway, and the brief discussion is made on avoiding serious geological trouble in course of route selection. The thoughts, comparison conditions and evaluation opinions introduced in this paper route selection can be used for reference to the survey and design of other mountain railways.