One of the commonly used methods for slope treatment in large-scale infrastructure projects such as airports and roads is to directly set slopes based on soil type and a certain slope. Although existing BIM software provides certain functions to meet the needs of toe line calculation and slope earthwork volume estimation, the repeated use of software functions during the parametric design process of airport terrain optimization results in high time costs and low efficiency. To address aforementioned issues, this paper proposes a method for calculating toe lines by establishing mathematical models of the slope and ground, and developing a Civil 3D plug-in using C# to realize automatic visualization generation of toe lines. Compared with the traditional manual drafting methods and existing BIM functionalities, it has the advantages of being suitable for computer solving and having fast calculation speed, which demonstrates high practical value for the projects that involve model generation and solution iteration.