In　order　to　study　the　effect　of　hydrodynamic　pressure　on　deep　water　bridge　under　seismic　action,　the　model　of　water-soil-single　pile　was　established　based　on　acoustic　element,　dynamic　local　artificial　boundary　and　fluid-solid　coupling　theory.　The　dynamic　response　of　structure　was　analyzed.　The　simplified　method　of　Morison　equation　simulation　and　the　anhydrous　model　were　used　to　analyze　the　difference　between　the　simplified　method　and　the　method　considering　the　fluid-solid　coupling　under　the　premise　of　pile-soil　interaction,　and　the　effect　of　hydraulic　pressure　on　pile-structural　dynamic　response.　On　the　basis　of　this,　the　dynamic　finite　element　model　of　the　water-soil-bridge　system　is　established　for　the　first　time　with　the　background　of　a　long-span　continuous　rigid　frame　bridge.　The　seismic　dynamic　response　of　the　water-soil-bridge　system　is　studied,　the　influence　of　hydrodynamic　pressure　on　the　seismic　response　of　deep　water　bridge　is　analyzed　and　compared　with　the　anhydrous　bridge　structure.　Influence　of　hydrodynamic　pressure　on　seismic　response　of　deep　water　bridge　was　studied.　The　results　show　that　the　effect　of　hydrodynamic　is　affected　by　the　seismic　wave　frequency,　but　the　rule　is　similar.　Under　the　same　external　condition,　the　influence　of　hydrodynamic　pressure　on　the　single　pile　is　larger　than　that　of　the　large　span　bridge　pile　due　to　the　influence　of　the　superstructure　and　the　interaction　of　pile　and　soil.　For　large　span　bridges,　the　effect　of　hydrody-namic　on　the　pile　foundation　in　water　is　larger　than　the　effect　on　piers　which　are　above　water.　And　the　internal　force　of　the　section　at　boundary　of　soil　and　water　increases　most.　After　considering　the　effect　of　hydrodynamic,　the　axial　force　of　beam　increases,　and　the　moment　of　beam　decreases.　Geohazards　risk　assessment　is　the　quantitative　analysis　and　evaluation　of　the　possibility　of　risk　regions　to　suffer　geological　disasters　of　different　intensities.　©　2018　Science　Press.　All　rights　reserved.