Carbon　nanotube　fiber　(CNTF)　is　an　assembly　of　carbon　nanotube　(CNT)　array　with　or　without　twisting.　The　interfacial　behavior　of　carbon　nanotube　fiber/polyethylene　(CNTF/PE)　composites　is　studied　by　using　molecular　dynamics　approach.　The　influence　of　the　geometrical　parameters　of　CNTF,　i.e.　fiber　length　and　chiral　number,　on　the　interfacial　interaction　of　the　composites　is　investigated.　Moreover,　the　interfacial　interaction　between　CNTs　is　studied　by　pulling　out　CNT　from　a　CNTF.　The　influence　of　twisting　of　CNTF　on　interfacial　interaction　between　CNTs　within　a　CNTF　as　well　as　between　CNTF　and　PE　matrix　is　analyzed.　The　uniform　interfacial　shear　force　and　the　sliding　failure　form　of　interface　are　exhibited　in　details.　It　is　shown　that　interfacial　energy　is　influenced　by　the　length　and　chiral　number　of　CNTFs.　While　the　interfacial　shear　force　is　independent　on　the　length　of　CNTFs,　but　it　increases　with　their　chiral　number.　Twisting　can　strengthen　the　interface　bonding　between　peripheral　CNTs　within　CNTF　but　weaken　that　between　the　central　CNT　and　its　surrounding　CNTs　as　well　as　between　CNTF　and　its　surrounding　PE　matrix.　(C)　2015　Elsevier　B.V.　All　rights　reserved.