High　cooling　water　tank　is　an　important　component　of　the　passive　containment　cooling　system　(PCS)　in　a　nuclear　island　building,　and　the　fluid-structure　interaction　(FSI)　between　cooling　water　and　shield　building　should　be　considered　in　dynamic　analysis.　The　FSI　effect　is　complex　and　it　will　take　a　long　computing　time　in　numerical　analysis,　a　simplified　method　needs　to　be　explored　to　improve　the　calculation　efficiency　under　the　condition　of　satisfying　a　certain　computing　accuracy.　Based　on　the　Housner　model,　a　simplified　liquid-tank　interaction　model　was　proposed,　which　could　be　used　in　the　dynamic　analysis　of　PCS　water　tank.　Three-dimensional　seismic　response　analyses　on　the　FSI　model　and　simplified　model　were　done　for　some　nuclear　island　building　by　using　ADINA　software.　The　peak　accelerations,　acceleration　spectra　of　floor　responses　and　effective　stresses　by　the　FSI　model　and　simplified　model　were　compared　and　the　relative　errors　were　analyzed.　The　results　show　that　the　proposed　simplified　liquid-tank　interaction　model　is　suitable　for　the　dynamic　analysis　of　nuclear　island　buildings　with　high　cooling　water　tank　under　three-dimensional　earthquake　actions,　and　good　results　of　the　simulation　of　FSI　effect　can　be　achieved.　©　2019,　Editorial　Office　of　Journal　of　Vibration　and　Shock.　All　right　reserved.