The　mechanical　behavior　of　coiled　tubing-in-riser　systems　is　critical　to　success　of　coiled　tubing　operations　in　the　development　of　offshore　oil　and　gas.　The　purpose　of　this　work　is　to　guide　the　coiled　tubing＇s　marine　applications　by　analyzing　influencing　factors　of　the　coupled　system.　This　paper　describes　a　mechanical　model　of　micro　elements　of　the　coiled　tubing-in-riser　system　under　force　excitation　of　ocean　loads.　Nonlinear　equations　simplified　by　finite　difference　method　are　solved　through　the　Newton-Raphson　iteration　method.　Then　the　analytical　analysis　is　compared　with　a　three-dimensional　finite　element　model　of　the　coiled　tubing-in-riser　systems.　To　ensure　safe　operation,　lateral　displacement　and　internal　bending　moment　of　the　riser　are　calculated.　Besides,　four　influencing　factors　annular　clearance,　ocean　depth,　platform　offset,　and　friction　coefficient　are　investigated.　The　results　show　that　strength　design　of　the　riser　needs　to　consider　the　critical　position,　and　larger　outer　diameter　of　coiled　tubing,　smaller　water　depth　operation,　smaller　platform　offset,　and　smaller　friction　coefficient　are　preferred　to　improve　the　injection　efficiency　of　coiled　tubing.　This　research　can　provide　important　theoretical　support　for　ocean　applications　of　coiled　tubing.