The　terminal　joints　of　the　steel　support　system　play　a　critical　role　in　controlling　the　deformation　and　stability　of　the　foundation　pit.　However,　accidents　caused　by　issues　with　these　terminal　joints　have　been　frequently　observed.　This　paper　introduces　the　Mold-bag　Concrete　Clamped　Joint　(MCCJ)　as　an　innovative　joint　for　enhancing　the　performance　of　terminal　joints　in　the　steel　support　system　of　subway　station　foundation　pit　projects.　Design　principles　of　MCCJ　in　the　steel　support　system　of　the　subway　station　foundation　pit　project　are　presented.　It　provides　a　detailed　explanation　of　its　structural　characteristics　and　working　principle,　as　well　as　elucidates　its　stress　situation　and　force　transmission　mechanism.　Three　MCCJ　specimens　were　designed　and　processed　for　indoor　compression　load　tests,　further　their　load-displacement　curves,　load-strain　curves,　and　failure　modes　were　obtained　and　analyzed　to　explore　the　load-bearing　performance　and　mechanical　characteristics　in　a　more　professional　and　academic　manner.　The　test　results　demonstrate　a　designed　bearing　capacity　of　over　4000kN,　exceeding　the　axial　design　bearing　capacity　of　Phi　609/630　steel　support　and　meeting　strong　joint　design　requirements.　Meanwhile,　a　refined　numerical　model　of　MCCJ　was　established　using　Abaqus,　validated　by　comparing　numerical　and　experimental　results.　Parameter　analysis　reveals　the　significant　influence　of　steel　tube　wall　thickness　and　connecting　flange　thickness　on　load-bearing　performance,　while　the　mold-bag　concrete　strength　grade　enhances　MCCJ　load-bearing　capacity　within　a　certain　range.　Furthermore,　to　fulfill　the　compatibility　between　MCCJ　and　existing　steel　supports,　and　achieve　joint　strength　and　high　performance,　the　parameter　optimization　directions　for　MCCJ　were　proposed.