Analytical　expressions　for　calculating　the　hydrodynamic　pressure　on　an　elliptical　hollow　cylinder　caused　by　outer　and　inner　water　under　earthquake　are　obtained.　Based　on　the　radiation　theory,　the　analytical　solutions　of　hydrodynamic　pressure　and　hydrodynamic　force　on　elliptical　hollow　cylinder　are　accurately　derived　by　assigning　reasonable　boundary　conditions　and　by　solving　the　Mathieu＇s　differential　equation　in　elliptical　coordinate　system.　Added　mass　expressions　distributed　over　the　height　of　the　cylinder　are　used　to　represent　the　hydrodynamic　interaction　effects,　which　are　extracted　from　the　hydrodynamic　force　expressions.　These　added　mass　expressions　are　so　complicated　that　lead　to　their　value　difficult　to　be　calculated.　Therefore,　these　added　mass　expressions　are　dealt　with　dimensionless　method　and　are　simplified　by　curve　fitting　method　in　this　study.　The　simplified　formulas　are　only　relevant　to　three　dimensionless　parameters　including　width-depth　ratio,　ratio　of　long　to　short　axis　of　the　ellipse　and　relative　distance　above　base.　The　calculation　results　show　that　the　simplified　formulas　are　in　good　agreement　with　the　analytical　solutions.