Based on the deep foundation pit of a river-crossing bridge pipe network in Xi’ an International Port Area, it crosses under the Xing-wei Station section of Metro Line 10. The influence of excavation-induced settlement of deep foundation pit in weak sand layer on the stability of existing structures under the support of Larsen steel sheet pile and steel support is explored. The three-dimensional model of deep foundation pit of pipeline network is established by using finite difference software FLAC3D, and the excavation, support and stability of deep foundation pit are completed. The simulation analysis of the stability of existing structures is carried out, and the law of soil deformation induced by deep foundation pit excavation is obtained. FALC simulation shows that the horizontal displacement of steel sheet pile in deep foundation pit excavation is symmetrically distributed under the action of Larsen steel sheet pile and steel support. The horizontal displacement of steel sheet pile increases first and then decreases with the buried depth. Under the action of steel support, the stratum displacement induced by deep foundation pit excavation is effectively weakened, and the horizontal displacement of steel sheet pile is reduced, which is convenient for controlling stratum deformation and is conducive to construction safety. The deep displacement deformation of soil induced by deep foundation pit excavation has little effect on the stability of existing bridges.