A　substructure　analysis　method　for　water-axisymmetric　cylinder　dynamic　interaction　problems　is　presented　to　simulate　the　seismic　response　of　water-structure　interactions.　According　to　the　wave　equation　and　boundary　conditions　for　the　three-dimensional　incompressible　water　and　by　applying　the　method　of　separation　of　variables,　the　model　is　transformed　into　a　two-dimensional　model,　which　is　analytical　in　the　circumferential　direction　and　numerical　in　the　vertical　and　radial　directions.　The　dynamic　stiffness　equation　of　the　infinity　water　at　the　truncated　boundary　is　derived　by　using　the　scaled　boundary　finite　element　method,　then　the　hydrodynamic　pressure　on　the　structure　can　be　obtained　by　coupling　the　finite　element　equation　of　the　near　field　water　with　the　hydrodynamic　on　the　truncated　boundary.　The　finite　element　equation　in　time　domain　of　a　water-axisymmetric　cylinder　interaction　system　is　developed　by　coupling　the　finite　element　equation　of　the　structure　with　the　hydrodynamic　pressure.　The　numerical　examples　demonstrated　that　the　proposed　method　is　accurate　and　efficient.　Numerical　results　show　that　the　effect　of　the　hydrodynamic　pressure　on　the　natural　frequency　and　the　dynamic　response　of　the　axisymmetric　structure　is　increasing　with　the　increase　of　the　water　depth　in　general.　Copyright　©2021　Engineering　Mechanics.　All　rights　reserved.