The　collapse　of　long-span　cable-stayed　bridges　under　strong　earthquakes　will　not　only　result　in　severe　casualties　and　loss　of　property　but　also　significantly　delay　the　rehabilitation　of　the　affected　area.　It　is　therefore　essential　to　study　the　failure　progress　and　potential　collapse　mechanisms　of　these　bridges　under　strong　earthquakes　for　assisting　their　inspection　and　maintenance　and　helping　them　survive　an　earthquake.　Collapse　simulations　in　existing　studies　are　commonly　conducted　with　design-document-based　finite　element　(FE)　models,　which　usually　neglect　the　actual　damage　state　of　the　bridges.　The　influences　of　modelling　uncertainties　on　the　simulated　responses　cannot　be　addressed.　This　study　proposes　a　nonlinear　FE　model　updating-based　collapse　prognosis　method　for　long-span　cable-stayed　bridges,　which　includes　(1)　a　correlated-updating-parameter-based　nonlinear　FE　model　updating　algorithm,　(2)　a　restarted　time　history　analysis-based　seismic　response　prediction　method　and　(3)　an　elemental　deactivation-based　collapse　simulation　algorithm.　The　shake　table　test　of　a　scaled　Sutong　cable-stayed　bridge　in　China　is　adopted　to　illustrate　the　proposed　earthquake-induced　collapse　prognosis　method.　A　refined　FE　model　of　the　bridge　is　first　established　and　nonlinearly　updated　using　the　measurement　data.　The　collapse　prognosis　of　the　bridge　under　a　subsequent　strong　ground　motion　is　then　performed　based　on　the　updated　model.　The　predicted　structural　responses　and　final　failure　mechanisms　are　compared　with　the　measured　responses　and　experimental　observations　with　good　agreement,　indicating　that　the　proposed　method　is　feasible　and　accurate　for　evaluating　the　seismic　performance　and　failure　mechanisms　of　long-span　cable-stayed　bridges.