The　dynamic　response　of　the　coiled　tubing　(CT)-in-riser　system　is　critical　to　the　success　of　offshore　CT　operations.　The　purpose　of　this　work　is　to　investigate　the　mechanical　behavior　of　the　CT　and　the　riser　and　analyze　the　influencing　factors　of　the　coupled　system.　This　paper　builds　dynamic　models　of　the　micro　elements　of　the　CT　and　the　riser,　and　then　a　coupled　model　of　the　CT-in-riser　system　is　presented　considering　the　excitation　of　ocean　loads　and　the　coupling　interaction　between　the　inner　pipe　and　the　outer　pipe.　The　dynamic　coupled　model　is　solved　by　the　finite　element　method.　A　finite　element　model　of　the　CT-in-riser　system　is　built　using　the　Abaqus/　AQUA　module.　The　effect　of　the　operating　parameters　including　the　top　injection　force,　the　top　tension,　the　platform　offset,　the　annular　clearance,　and　the　friction　coefficient,　and　the　environmental　parameters　including　the　ocean　depth,　current　speed,　wave　period,　and　wave　height　are　discussed.　The　results　show　that　the　top　tension　should　be　properly　controlled;　the　platform　offset　and　friction　coefficients　should　be　reduced;　the　annular　clearance　should　be　appropriately　reduced;　a　low　current　speed　and　wave　height　should　be　selected　for　operation;　and　the　wave　period　and　wave　height　have　a　little　effect　on　the　CT　axial　force.　This　research　can　provide　important　theoretical　support　for　the　offshore　CT　application.