Abstract: To improve the BIM (Building Information Modeling) design efficiency of railway subgrade retaining engineering, this paper constructed a parametric modeling algorithm for subgrade retaining wall structures and developed parametric BIM design software based on the BIMBase platform. At the geometric semantic parsing level, the paper established the logical workflow of parametric modeling, semantically decomposed typical section outlines of subgrade retaining wall structures, identified their core control parameters, investigated dynamic correlation rules among various parameters, and formulated the parametric modeling algorithm for subgrade retaining wall structures. At the data structure construction level, the paper derived an abstract base class from graphic objects. On the basis of semantic parsing results, it fully defined the base class and its derived classes. At the design program implementation level, the paper carried out engineering implementation on BIMBase and developed a fully functional BIM design program module by integrating the professional railway design workflow. Verification results demonstrate that the proposed method effectively meets the practical BIM design requirements of subgrade retaining engineering and significantly improves modeling efficiency and the reusability of models across different projects.