In　recent　years,　deep　geothermal　energy　has　become　a　solid　option　for　building　heating　worldwide.　For　the　densely　populated　urban　area,　a　novel　closed-loop　system　of　the　deep　U-type　borehole　heat　exchanger　(DUBHE)　has　attracted　attention　in　northern　China.　In　order　to　achieve　the　evaluation　of　geological　parameters　on　the　long-term　performance　of　DUBHE,　thermal　conductivity,　geothermal　gradient,　specific　heat　capacity,　groundwater　flow　direction,　and　Darcy　velocity　are　selected　in　this　paper　and　all　the　parameters　are　set　in　three　levels.　And　orthogonal　test　L18(35)　is　established　by　adopting　the　Taguchi　method　for　the　reduction　of　simulation　time　cost.　Three　evaluation　indexes　are　introduced　to　investigate　the　impacts　of　geological　parameters　on　the　performance　of　DUBHE　and　obtain　the　optimal　set,　including　average　outlet　temperature　Tout,　maximum　cumulative　heat　extraction　amount　Qtotal　and　soil　temperature　decay　rate　Dsoil.　Results　show　that　the　geothermal　gradient　has　the　most　significant　effect　on　Tout　and　Qtotal,　and　its　contribution　degree　is　70.14%　and　62.10%　respectively.　As　for　the　Dsoil　index,　the　most　influential　parameter　is　specific　heat　capacity　and　the　corresponding　contribution　ratio　is　92.41%　determined　by　the　analysis　of　variance　(ANOVA)　method.　For　the　optimized　combination　by　adopting　matrix　analysis,　the　Tout　reaches　33.92　°C,　the　Qtotal　is　284.08　TJ　and　the　Dsoil　of　the　optimized　scenario　is　12.66%　after　the　long-term　operation.　In　addition,　according　to　the　orthogonal　test　results,　this　study　intuitively　discusses　the　potential　of　carbon　emission　reduction　for　the　DUBHE　under　the　typical　geological　conditions　in　northern　China.　The　study　results　presented　in　this　work　can　guide　the　system　design　of　DUBHE　and　serve　as　the　reference　for　the　decision-maker　in　the　application　of　deep　geothermal　heating　technology.　©　2022　Elsevier　Ltd