Vertical　cylinders　are　widely　used　as　supporting　structures　in　ocean　engineering　applications.　Shock　waves　due　to　underwater　explosives　(UNDEX)　can　cause　serious　damage　to　offshore　structures,　which　has　attracted　the　interest　of　many　researchers.　The　propagation　characteristics　of　shock　waves　produced　by　UNDEX　across　a　cylinder　are　a　complex　physical　phenomenon　that　involves　fluid-structure　dynamic　interactions.　For　the　shock　wave　produced　by　UNDEX,　the　total　pressure　on　a　cylinder　consists　of　three　parts,　including　the　incident　shock　wave　pressure,　scattered　wave　pressure　and　radiation　pressure　due　to　the　motion　of　the　cylinder.　This　paper　develops　an　improved　method　for　obtaining　the　transient　response　of　a　vertical　circular　cylinder　subjected　to　UNDEX.　First,　an　empirical　formula　of　the　shock　wave　pressure　for　far-field　UNDEX　is　adopted　as　the　incident　shock　wave.　Based　on　the　continued　fraction　(CF)　expansion　of　the　frequency-domain　dynamic　stiffness　coefficient,　an　accurate　model　in　the　time　domain　for　solving　the　scattered　wave　pressures　on　a　cylinder　is　further　developed.　Then,　the　added　mass　model　is　used　to　replace　the　fluid-structure　interaction　caused　by　radiation　wave.　Finally,　the　vibration　equation　of　a　Euler-Bernoulli　beam　is　utilized　to　evaluate　the　transient　response　of　the　cylinder　subjected　to　UNDEX.