To reduce the incidence of engineering accidents caused by foundation pit failures, the influencing mechanism of local failures such as support failure and soil leakage in the foundation pit with internal braced row pile support was investigated by model test. The results show that the axial force of the support increases with the deepening of the foundation pit excavation. The increment of the axial force of the support near the middle of the foundation pit is the largest, whereas that near the pit corner is the smallest. In the case of local failure of the support, part of the load is transferred to the adjacent support through the purlin, and the other part of the load is transferred to the displacement coordination of the support structure. When all the support fail, the overall stiffness of the support structure decreases, and the support system becomes cantilever row pile support. The displacement, bending moment of the support pile and the settlement of the soil outside the pit increase significantly compared with that before the overall failure of the support system. When the local soil behind the pile leaks, the soil quickly collapses and flows into the bottom of the pit to form a soil pile, creating a large area of collapse outside the pit, which has a great impact on the surrounding environment and construction.