A　prefabricated　concrete-filled　steel　tube　(P-CFST)　bracing　was　applied　for　the　top　internal　support　of　supporting　structure　aiming　at　the　difficulties　of　deep　excavated　depth　and　narrow　working　space　in　the　excavation　engineering　of　a　shield　shaft　for　Line　17　of　Beijing　Subway.　The　interval　among　bracings　were　enlarged　by　using　P-CFST　bracing　resulting　in　being　convenient　for　excavation　and　bracing　erection.　The　whole　process　of　excavation　and　support　was　simulated　with　a　three-dimensional　finite　element　model　by　ABAQUS.　Systematic　monitoring　for　axial　force　of　bracing,　deformation　of　fender　piles,　displacement　of　pile　top　and　ground　settlement　were　accomplished　in　implementary　process　of　excavation.　The　security　of　excavation　in　combined　support　of　P-CFST　bracing　and　steel　bracing　was　ensured.　The　spatial　effect　on　deformation　of　supporting　structure,　surface　of　ground　settlement　and　axial　force　of　different　bracing　was　analyzed.　The　simulation　and　monitoring　results　indicated　that　the　deformation　in　same　deep　of　supporting　structure　manifested　shape　of　parabola　or　basin,　and　scope　of　spatial　effect　on　deformation　of　supporting　structure　was　less　than　8　m.　Contour　line　of　ground　settlement　near　foundation　pit　changed　from　arc　to　trapezoid.　The　location　of　biggest　settlement　first　moved　further　and　then　moved　back.　Axial　force　of　P-CFST　bracing　was　more　sensitive　than　steel　bracing　under　influence　of　excavation　and　bracing　erection.　Design　interval　among　bracings　can　be　enlarged　by　applying　high-powered　P-CFST　bracing　in　first　internal　support,　and　deformation　of　supporting　structure　and　stratum　may　be　effectively　controlled.　©　2019,　Zhejiang　University　Press.　All　right　reserved.