Super-stretchable　helical　structures　made　from　carbon　nanotube　(CNT)　fibers　are　promising　candidates　for　applications　in　stretchable　and　wearable　devices.　A　multi-scale　model　of　the　helical　structures　of　CNT/polymer　composite　fibers　is　presented　to　gain　more　insight　into　their　deformation　properties　and　damage　mechanisms.　By　imitating　the　practical　preparation　process,　a　suitable　model　for　the　helical　structures　is　obtained,　which　reflects　the　features　of　both　the　macro-scale　geometric　construction　and　the　micro-scale　structure.　An　interpretation　of　the　stress-strain　curves,　various　potential　energies　caused　by　micro-structural　evolution,　and　the　fracture　morphology　are　conducted.　In　addition,　the　role　of　the　strain　rate　on　the　mechanical　behavior　of　the　helical　structures　is　investigated.　It　is　found　that　the　elongation　of　the　helical　composite　fibers　can　reach　100%-300%,　depending　on　the　pitch　of　the　helix　and　the　tensile　strain　rate.　The　specific　strength　of　the　helical　composite　fibers　greatly　decreases　for　a　decreasing　helix　pitch.　The　deformation　mechanisms　are　divided　into　four　types　according　to　different　predominate　factors,　for　different　strain　rates.　This　work　contributes　to　the　understanding　of　the　deformation　and　damage　mechanisms　behind　the　superstretchability　and　great　stability　of　the　helical　structures　of　CNT/polymer　composite　fibers.　(C)　2017　Elsevier　Ltd.　All　rights　reserved.