The　interfacial　behavior　of　carbon　nanotube　fiber　(CNT　fiber)　composites　is　studied　by　using　an　experiment　of　fiber　pulling-out　from　a　polymer　microdroplet　and　cohesive　finite　element　method.　A　clamping　fixture　based　on　nano-tensile　test　system　was　designed　for　the　microdroplet　test　of　interfacial　properties　of　the　composites.　Force-displacement　curves　and　shear　strengths　of　the　interface　between　CNT　fibers　and　polymers　were　obtained.　Then　an　experiment-based　cohesive　finite　element　model　was　established　to　simulate　the　debonding　and　slipping　of　interface　between　the　CNT　fiber　and　polymer.　Calculated　force　displacement　curves　for　fiber　pullout　from　microdroplet　are　comparable　with　the　experimental　data.　The　debonding　strength　and　failure　feature　of　the　interface　of　CNT　fiber　composite　were　discussed.　It　is　found　that　the　looseness　of　CNT　fiber　assembled　by　CNT　bundles　and　threads　leads　to　relatively　low　interfacial　strength,　which　is　very　different　from　the　traditional　continuum　-block　fiber　composites.　(C)　2017　Elsevier　Ltd.　All　rights　reserved.