To address the issues of low openness of geometric engines and technology bottlenecks in universal building information modeling (BIM) platforms, the author proposes a BIM modeling method based on BIMBase for lining structures of mountain-crossing railway tunnels. The Chinese graphics engine is developed using C++, and the BIM forward design software for tunnel lining is implemented through data structure definition, parameterized component development, and interactive function implementation. The modeling accuracy meets the full lifecycle application requirements covering the railway engineering design, construction, and operation stages. The research results demonstrate the following: (1) Data structure definition: by combining the BIMBase engine kernel architecture with lining topology characteristics, the graphic object base class is derived to construct a single-layer lining data structure. (2) Parameterized component development: a parameterized cross-section profile design algorithm is developed using geometric semantic analysis. This algorithm is independent of any graphic engine and facilitates component development through the instantiation of abstract base classes and virtual function overriding using the BIMBase engine architecture kernel-layer interfaces, developing complete three-dimensional (3D) single-layer lining structure components. (3) Interactive function implementation: an assignment method for the cross-sectional properties of lining structures suitable for multilayer mined and single-layer open-cut tunnels, as well as high-precision sweeping path fitting techniques adaptive to spatial line curvature changes, are analyzed. Through the implementation of the IToolProperty interface, the BIM model properties and interactive linkage updates for 3D geometry are synchronized, ultimately creating BIM forward-design software for mountain-crossing railway tunnel lining structures.