Centered　on　the　characteristics　of　deep　excavation　engineering　for　open-cut　subway　station　projects,　a　fabricated　inner-bracing　system　of　concrete-filled　steel　tube,　which　consisted　of　normal　straight　components,　short　components,　connection　joints,　etc.,　was　developed.　Based　on　the　features　of　inner-bracing　stress　and　structure,　the　internal　force　calculation　formulas　were　derived　from　all　the　components.　Referring　to　the　specifications　of　concrete-filled　steel　tube　and　the　formulas　of　column　stability,　several　calculation　methods　of　bearing　capacity　for　the　supports　and　ring-shape　purlin　were　proposed.　The　mix　proportion　of　filled　concrete　was　designed,　and　the　concrete　physical,　working　and　mechanics　properties　were　detected　by　material　tests,　and　then　the　lightweight,　slight　expansion　and　self-compacting　concrete　were　prepared　as　the　inner-bracing　filling　material.　Taking　a　deep　excavation　engineering　of　a　station　project　in　Beijing　Subway　as　a　case,　the　inner-bracing　system　of　normal　section　foundation　pit　was　designed　and　studied.　The　results　show　that　the　calculation　methods　of　inner-bracing　system　design　is　reasonable　and　reliable,　and　the　designed　inner-bracing　system　meet　the　requirements　of　excavation　support　force　and　foundation　pit　stability.　©　2016,　Editorial　Department　of　Journal　of　Beijing　University　of　Technology.　All　right　reserved.