Coiled　tubing　(CT)　is　prone　to　helical　post-buckling　with　variable　pitch　when　being　operated　in　deep　water.　The　influence　of　ocean　load　on　the　axial　force　of　a　variable　pitch　pipe　is　complex　and　lacks　relevant　research.　In　this　study,　a　＂pipe-in-pipe＂　system　test-bed　was　established　for　simulation　experiments.　Based　on　the　experimental　results,　a　mechanical　analysis　of　the　CT＇s　buckling　model　is　carried　out.　The　effects　of　different　ocean　loads　and　helical　post-buckling　configurations　on　the　axial　force　are　studied.　The　results　show　that　the　greater　the　amplitude　of　ocean　load　and　the　degree　of　helical　post-buckling,　the　greater　is　the　axial　force　fluctuation　of　the　CT.　Because　the　buckling　configuration　is　of　variable　pitch,　the　decrease　in　the　axial　force　is　different　when　ocean　loads　with　the　same　size　and　opposite　direction　are　applied.　Besides,　with　the　increase　in　the　helical　postbuckling,　the　pitch　gradually　changes　from　variable　pitch　to　equal　pitch,　and　the　pitch　number　increases.　The　research　results　are　helpful　to　the　supplement　of　CT＇s　buckling　system.