A　comprehensive　investigation　of　the　mechanical　behavior　and　microstructural　evolution　of　carbon　nanotube　(CNT)　continuous　fibers　under　twisting　and　tension　is　conducted　using　coarse-grained　molecular　dynamics　simulations.　The　tensile　strength　of　CNT　fibers　with　random　CNT　stacking　is　found　to　be　higher　than　that　of　fibers　with　regular　CNT　stacking.　The　factor　dominating　the　mechanical　response　of　CNT　fibers　is　identified　as　individual　CNT　stretching.　A　simplified　twisted　CNT　fiber　model　is　studied　to　illustrate　the　structural　evolution　mechanisms　of　CNT　fibers　under　tension.　Moreover,　it　is　demonstrated　that　CNT　fibers　can　be　reinforced　by　enhancing　intertube　interactions.　This　study　would　be　helpful　not　only　in　the　general　understanding　of　the　nano-and　micro-scale　factors　affecting　CNT　fibers＇　mechanical　behavior,　but　also　in　the　optimal　design　of　CNT　fibers＇　architecture　and　performance.