During　the　construction　of　deep　and　large　foundation　pits　in　floodplain　areas,　it　is　inevitable　to　cause　stratum　disturbance　and　endanger　the　safety　of　the　surrounding　environment.　This　paper　focuses　on　the　influence　of　deep　foundation　pit　excavation　on　surrounding　environment　based　on　a　soft　soil　deep　foundation　pit　project　in　Nanjing　floodplain　area.　A　series　of　laboratory　tests　were　conducted　to　obtain　the　parameters　of　the　small　strain　hardening　(HSS)　model　for　the　typical　soil　layers.　Then　PLAXIS　3D　software　is　used　to　simulate　the　excavation　process　of　the　foundation　pit.　On　the　basis　of　field　measurement　and　numerical　model,　the　deformation　characteristics　of　deep　foundation　pit　and　surrounding　environment　are　analyzed.　The　HSS　model　and　the　appropriate　model　parameters　can　effectively　simulate　the　deformation　behavior　during　the　excavation　of　the　foundation　pit.　Aiming　at　the　problem　of　excessive　deformation　of　foundation　pit　and　surrounding　pipelines,　the　reinforcement　effect　of　reinforced　soil　in　active　and　passive　areas　under　different　reinforcement　parameters　is　analyzed.　The　optimal　reinforcement　width　and　depth　should　be　determined　after　reasonable　analysis　to　obtain　the　best　economic　benefits.