Guangxi Baise to Jingxi highway is an important part of the highway network in Guangxi region. It is located in the southwest of Guangxi area, where terrain is complex, with low mountain area as the main body, and the karst valley and karst gullies scattered in the mountains. In view of the complex terrain and geologic conditions of this project, route design is crucial for the project cost, and lots of matters need to be solved during the construction. This paper probes into the overall route optimized design for the mountainous highway focusing on the construction of the project mentioned.