The　pipe-in-pipe　structure　is　one　of　the　most　effective　ways　for　deep-sea　oil　and　gas　transportation.　In　this　paper,　the　global　mechanical　model　of　a　deep-sea　J-laying　pipe-in-pipe　was　established　by　fully　considering　the　coupling　connection　of　inner　and　outer　pipes　and　the　dynamic　interaction　between　the　outer　pipe　and　seabed　soil.　The　validity　of　the　numerical　model　was　verified　by　comparison.　The　global　dynamical　response　analysis　of　the　J-laying　pipe-in-pipe　was　carried　out　under　the　combined　action　of　random　waves,　ocean　currents　and　pipelay　vessel　motions　in　a　deep-sea　environment.　The　dynamic　response　characteristics　of　the　outer　and　inner　pipes　of　the　pipe-in-pipe　were　obtained,　and　the　influence　of　the　centralizer　stiffness　and　the　diameter-thickness　ratio　of　the　outer　and　inner　pipes　on　the　force　and　deformation　responses　of　the　pipe-in-pipe　was　further　explored.　The　results　show　that　the　increase　of　centralizer　stiffness　leads　to　an　increase　of　the　tension　response　amplitude　ratio　of　the　outer　pipe　to　the　inner　pipe.　The　diameter-thickness　ratios　of　outer　and　inner　pipes　also　have　a　great　influence　on　the　corresponding　tension,　bending　moment,　stress　and　strain　response　amplitude　ratios.　The　analytical　results　can　provide　a　theoretical　basis　for　the　design　and　construction　of　deep-sea　J-laying　pipe-in-pipes.　©　2023　China　Ship　Scientific　Research　Center.　All　rights　reserved.