Similar　material　model　test　and　numerical　simulation　method　were　used　to　study　the　reinforcement　effect　of　isolation　piles　on　the　existing　shield　tunnel　structure　in　the　adjacent　building　construction　for　analyzing　foundation　pit　excavation　and　new　building　construction　approaching　existing　shield　tunnel　engineering.　The　numerical　simulation　orthogonal　experiment　was　used　to　optimize　four　isolation　pile　parameters.　The　conclusions　were　obtained　as　follows:　(1)　Isolation　piles　could　share　horizontal　load　of　the　soil　at　the　rear　side　of　the　support　structure　and　reduce　horizontal　displacement　of　the　soil.　As　a　result,　maximum　horizontal　displacement　of　the　tunnel　structure　and　differences　in　horizontal　displacement　between　the　tunnel　structure　roof　and　the　floor　after　foundation　pit　excavation　and　building　loading　were　decreased.　The　horizontal　displacement　and　torsional　deformation　of　the　tunnel　structure　toward　the　direction　of　the　foundation　pit　were　controlled,　and　the　increase　in　internal　forces　of　the　transverse　tunnel　structure　was　also　restrained.　(2)　At　the　elevation　above　the　tunnel　roof,　the　increase　in　burial　depth　of　the　isolation　pile　top　slightly　affected　the　reinforcement　effect　on　the　tunnel　structure.　The　increase　in　burial　depth　of　the　isolation　pile　bottom　could　improve　the　reinforcement　effect.　Thus,　burial　depth　of　the　isolation　pile　bottom　should　be　properly　increased　in　the　engineering　practice.　The　reduction　in　pile　spacing　could　improve　the　reinforcement　effect.　Accordingly,　pile　spacing　should　be　properly　selected　in　the　engineering　practice.　With　the　increase　of　diameter　of　the　isolation　pile,　the　reinforcement　effect　of　isolation　piles　increased　obviously.　(3)　Pile　diameter　had　the　greatest　influence　on　the　reinforcement　effect　of　isolation　piles,　followed　by　burial　depth　of　the　pile　bottom,　pile　spacing,　and　burial　depth　of　the　pile　top.　Orthogonal　experiments　indicated　the　following　optimal　parameter　values:　a　pile　diameter　of　1.2　m,　a　burial　depth　of　the　pile　bottom　of　2H,　a　pile　spacing　of　1.6　m,　and　a　burial　depth　of　the　pile　top　of　0.75Z.