In　this　paper,　combining　with　the　field　ambient　vibration　tests　and　finite　element　(FE)　model　updating,　a　dynamic-based　evaluation　method　is　proposed　and　adopted　to　predict　the　load-carrying　capacity　of　a　prestressed　concrete　cable-stayed　bridge　with　single　tower　under　the　current　condition　and　several　possible　damage　conditions.　It　is　demonstrated　that　the　cable-stayed　bridge　can　satisfy　the　design　requirements　and　the　adjustment　of　cable　forces　is　not　needed　under　the　current　condition.　The　results　also　reveal　that　over-loading　and　the　area　discount　of　stay-cables　caused　by　cautery　make　great　influence　on　the　load-carrying　capacity　of　the　bridge.　This　kind　of　evaluation　can　serve　as　a　basis　for　the　long-term　health　monitoring,　maintenance　and　rehabilitation　and　it　has　great　importance.