In view of the influence of deep and large foundation pit construction on the safety of existing subway struc-tures,this paper takes the actual project as an example,analyzing the influence of foundation pit excavation on existing subway structures through theoretical analysis and three-dimensional numerical simulation.The re-sults show that the excavation of foundation pit will cause deformation and non-uniform settlement of subway structure.Therefore,only by strictly following the design plans and adopting reliable methods during construc-tion can the safety of existing structures be guaranteed.