Abstract: Long-Bai Rail starts from the Longchang Station of Chengyu Rail in Sichuan Province to the north, going through Luzhou, Bijie of Guizhou to the south and linking at Huangtong to Gui(Guiyan)-Kun(Kunming)Rail. It further goes to the south through the east of Nanzhou of the west Guizhou Province and finally ends at Baise of the Guangxi Autonomous Region to Nan(Nanning)-Kun(Kunming)Rail. The total length is 800 km.From the view of regional conditions by comparing and analyzing, as well sa the actual demands of economic development of the great southwest area, the rail should constructed as soon as possible. The reasons are as follows:1. It is the main access of the southwest economic core area to the sea. It will provide better conditions for open door and various international economic and trade relationship.2. It is the short-cut of many provincial capital cities and major economic centres of the great southwest area. The rail would be convenient for the inter-linkages among them.3. Its construction will fasten the development of areas with advanced mining resources along the rail. It is the requirements to ensure the national economic sustainable development of the southwest area and certain parts of South China.4. The construction of the rail will decentralize the volume of nearby rails, which are at their saturation. It will be an indispensable major rail to improve the network of the great southwest area.5. It will play an important role in helping the poverty reduction along the railway.