Abstract: a　2dhydrodynamic 　real －time 　forecasting　model　for　pearl　river　delta　considering　the 　interaction 　among　floodtide 　and　storm　surge　built　based　on　the　demands 　efficienc y　and　accurac y．the　study area 　of 　the　model　covers　whole　river 　networkei ght 　river　mouths　of 　the　delta　and　the 　sea　bay．the　finitevolume　method　based　on　unstructured　mesh　adopted 　to 　insure　mass　conservation．by　introducing　asemi －implicit 　eulerian－lagrangian 　al gorithm　to 　the　process 　of 　solving　shallow　water　equationsthecomputational 　efficienc y　improved．by　combining　the 　tide 　and　storm　surge　model　of 　south　china　seato　get 　the　offshore 　boundary　and　using　re gression 　coefficient　method　to 　correct　mannings　coeffi－cientsthe　precision　of 　the　numerical 　solution 　is 　effectivel y　advanced．flood　and　storm　surge　real －timeforecasting　system　pearl　river　delta　developed　based　on　three－tier 　browserserver 　framework．it 　inte grates 　the 　components　of 　simulation visualization 　and　anal ysis 　using　web　services　and　webgistechnolo gies．the 　application 　of　typhoon　hagupit200814 forecasting　indicates 　the　key　technologies 　presented 　in　paper 　can 　improve 　the 　efficienc y　and　accurac y　of 　flood 　and　storm　surge　forecasting　tosome 　extent．