A case study of the SichuanTibet railway′s Shergyla Mountain tunnel is conducted to improve the construction quality of the invert of the singletrack railway tunnel constructed by drilling and blasting method and the environment in the tunnel, as well as promote green construction of the prefabricated structures. Further, the structural form, circumferential and longitudinal connections, waterproofing, assembling equipment, tunnel bottom filling, construction technology, and economic benefits of the prefabricated invert are studied. The main research conclusions are as follows: (1) The invert and the filling layer are integrally prefabricated into a monolithic hollow structure with a good stress condition that is easy to be assembled in the tunnel. (2) The prefabricated block is connected with the castinsitu secondary lining using square tongue and groove or square tongue, groove, and reserved steel. The prefabricated block is longitudinally squeezed by tensioning and finishing rolling rebar, and its underside is treated with crushed stone and backfill groutingcushion. The prefabricated invert is used in the SichuanTibet railway′s Shergyla Mountain tunnel, allowing for rapid and mechanized construction of the undertrack structure, which improves the overall level of mechanized construction of mountain railway tunnels.