A　response　surface　method-based　fragility　analysis　method　of　mega-sub　controlled　system　is　proposed.　Four　ultimate　damage　state　for　mega-sub　controlled　system　are　defined,　and　based　on　which,　a　method　for　solving　the　limit　values　of　the　four　performance　levels　is　put　forward.　Considering　the　uncertainties　of　ground　motions　characteristics　and　structures　parameters,　this　paper　proposes　a　fragility　analysis　method　of　mega-sub　controlled　system　based　on　RSM　(response　surface　method).　Using　central　composite　design　method　to　construct　a　series　of　samples　for　various　ground　motions　and　mega-sub　controlled　structures,　nonlinear　dynamic　time　analysis　of　the　sample　model　was　carried　out　by　SAP2000,　and　substructures　response　surface　model　of　mega-sub　controlled　structure　were　built,　then　the　fragility　curves　were　obtained　using　of　Monte　Carlo　method,　and　the　damaging　probability　of　mega-sub　controlled　structure　are　given,　provides　the　basis　for　damage　assessment,　and　is　of　great　engineering　application　prospects.