The　coiled　tubing　(CT)　rotary　operation　is　a　new　technology　being　explored　in　the　industry,　where　relevant　research　on　the　top　torque＇s　influence　on　the　CT　during　rotary　operation　is　missing.　An　indoor　CT　offshore　rotary　operation　physical　simulation　system　was　built.　Through　theory　and　experiment,　the　influence　of　torque　on　the　CT＇s　axial　force　transmission　characteristics　in　the　offshore　＇pipe　in　pipe＇　system　is　studied.　The　results　show　that　the　small　constant　torque　applied　at　the　CT　top　will　not　directly　lead　to　string　instability.　However,　the　small　constant　torque　applied　at　the　CT　top　will　reduce　the　limit　loads　of　sinusoidal　and　helical　buckling,　leading　to　string　instability　at　an　earlier　stage.　Additionally,　it　is　shown　that　torque　would　accelate　string　instability　whereas　the　small　top　torque　has　little　effect　on　the　CT＇s　axial　force　transfer　efficiency.　The　research　results　will　help　to　establish　the　theoretical　guidance　system　of　the　CT　offshore　rotary　operation.