An　accurate　added　mass　model　representation　for　a　flexible　elliptical　cylinder　vibrating　in　water　is　presented.　To　accomplish　this,　the　analytical　expressions　for　the　hydrodynamic　forces　on　elliptical　cylinders　are　first　derived　in　the　elliptical　coordinate　system.　Then,　explicit　expressions　for　computing　the　free　vibration　response　of　the　elliptical　cylinder　vibrating　in　water　like　natural　frequencies　and　mode　shapes　are　given　by　solving　the　coupled　differential　equations.　The　expressions　for　calculating　the　forced　vibration　responses　of　a　flexible　cylinder　surrounded　by　water　are　further　given.　However,　the　expressions　of　the　exact　model　are　too　complicated　and　require　the　use　of　computer　program　to　generate　the　results.　Based　on　the　fundamental　frequency　reduction　rate,　a　simple　formula　for　the　added　mass　representation　is　proposed　to　simulate　a　flexible　elliptical　cylinder　vibrating　in　water.　The　simple　formula　for　evaluating　the　natural　frequencies　and　the　simple　model　for　evaluating　the　seismic　responses　of　the　submerged　cylinder　are　also　presented　in　the　study.