The　stability　of　tunnel　surrounding　rock　is　the　mainly　concerned　content　during　tunnel　design　and　construction　procedure.　It　is　one　of　the　main　tasks　for　researchers　to　accurately　estimate　the　stability　of　tunnel　surrounding　rock.　Generally,　determined　by　its　engineering　geological　features,　surrounding　rock　of　mountain　tunnel　is　cut　by　joints　into　discontinuous　blocks,　which　can　be　more　accurately　analyzed　by　discontinuum-base　numerical　methods,　e.　g.,　the　discontinuous　deformation　analysis　(DDA)　method.　In　addition,　progress　of　deformation　and　failure　of　tunnel　surrounding　rock　is　often　a　nonlinear　catastrophe　behavior,　so　that　it　is　feasible　to　determine　the　tunnel　stability　by　the　catastrophe　theory.　The　strength　reduction　method　can　be　used　to　simulate　failure　progress　development　in　its　computation　procedure　by　reducing　the　strength　parameters.　Based　on　the　DDA　method,　the　strength　reduction　method　and　the　catastrophe　theory　are　adopted　to　study　the　stability　of　tunnel　surrounding　rock.　Firstly,　the　strength　reduction　method　is　used　to　obtain　the　function　of　displacement　and　the　reduction　factor　varies,　and　then　the　catastrophe　theory　is　used　to　judge　the　critical　state　of　surrounding　rock　based　on　the　function　curve.　The　reduction　factor　at　this　critical　point　is　defined　as　the　stability　safety　factor　of　the　tunnel.　Thus　the　stability　status　of　the　surrounding　rock　can　be　determined.　Jinjishan　multiple-arch　tunnel　is　a　big　span　tunnel　with　eight　traffic　lanes,　which　is　a　very　important　project　of　the　second　phase　project　of　Fuzhou　city　airport.　This　method　is　put　into　application　of　this　project　to　guarantee　safety　of　the　tunnel.