To study the deformation evolution of weathered rock and soil strata in deep excavation pits, Based on a subway deep excavation project in Changsha, a three-dimensional numerical model was established by using PLAXIS 3D. The influence of excavation depth, load position, and load magnitude on the deformation of deep excavation pits during the excavation process were analyzed. The research results indicate that in the excavation process of subway foundation pits in weathered rock and soil, deformation mainly occured in the soil layer. When the load of 20 kN/ m2 and 5 m away from the pit, the maximum lateral displacement of the retaining pileis was 0.72 mm. When the load reaches reached 60 kN/ m2, the maximum settlement of the ground surface was 70.9 mm. These results can serve as a reference for the design of foundation pits in similar weathered rock and soil conditions.