Wearable　and　stretchable　electronics　including　various　conductors　and　sensors　are　featured　with　their　lightweight,　high　flexibility,　and　easy　integration　into　functional　devices　or　textiles.　However,　most　flexible　electronic　materials　are　still　unsatisfactory　due　to　their　poor　recoverability　under　large　strain.　Herein,　we　fabricated　a　carbon　nanotubes　(CNTs)　and　polyurethane　(PU)　nanofibers　composite　helical　yarn　with　electrical　conductivity,　ultrastretchability,　and　high　stretch　sensitivity.　The　synergy　of　elastic　PU　molecules　and　springlike　microgeometry　enable　the　helical　yarn　excellent　stretchability,　while　CNTs　are　stably　winding-locked　into　the　yarn　through　a　simple　twisting　strategy,　making　good　conductivity.　By　virtue　of　the　interlaced　conductive　network　of　CNTs　in　microlevel　and　the　helical　structure　in　macrolevel,　the　CNTs/PU　helical　yarn　achieves　good　recoverability　within　900%　and　maximum　tensile　elongation　up　to　1700%.　With　these　features,　it　can　be　used　as　a　superelastic　and　highly　stable　conductive　wire.　Moreover,　it　also　can　monitor　the　human　motion　as　a　rapid-response　strain　sensor　by　adjusting　the　content　of　the　CNTs　simply.　This　general　and　low-cost　strategy　is　of　great　promise　for　ultrastretchable　wearable　electronics　and　multifunctional　devices.