An　open　excavation　order　method　is　used　in　the　deep　strip　foundation　pit　of　a　underground　station　neighboring　railway　and　the　outer　edge　of　the　pit　enclosure　structure　from　the　center　line　of　the　railway　is　from　8　m　to　12　m.　According　to　construction　conditions,　the　pit　and　railway　change　laws　with　the　cast-in　place　pile　system　supported　by　a　steel　brace　are　studied　by　analyzing　and　comparing　monitoring　data　during　the　initial　digging　stage.　Deformation　features　of　monitoring　data　curve　about　the　deep　horizontal　displacement,　horizontal　displacement　of　the　pile　tip,　axial　force　of　the　steel　brace,　vertical　displacement-time　of　props,　and　settlement　of　the　railway　are　summarized.　The　main　reasons　of　abnormal　variation　in　curve　are　analyzed　to　guide　the　construction　to　control　excavation　deformation.　Therefore,　the　pit　foundation　safety　and　railway　normal　operation　during　the　subsequent　cut　stages　are　ensured.