Addressing the stability challenges of foundation pit engineering in highway construction, this study uses a real project as an example to describe a standardized construction process for foundation pit operations and employs numerical simulation to validate the scheme"s rationality. First, support selection was optimized based on geological survey data; then a three-dimensional geological model was established using Midas GTS finite element software to simulate the foundation pit support structure response under various construction conditions; finally, the control effect of the support system was analyzed in depth from three dimensions: diaphragm wall displacement, internal forces and deformations of the supports, and surrounding stratum settlement. The study shows that the scheme is safe and controllable, and the relevant conclusions not only provide theoretical support for this project but also offer scientific basis for foundation pit engineering under similarly complex geological conditions.