A　novel　3D　nanostructure　which　can　be　potentially　applied　in　reinforcement　of　composites　with　enhanced　interfacial　adhesion　is　constructed　by　orderly　connecting　carbon　nanotubes　(CNTs)　of　different　lengths.　A　representative　element　(RE)　of　CNTs　and　unique　assembly　method　of　the　desired　3D　nanostructures　are　described　in　detail.　It　is　validated　by　the　first　principle　that　the　present　nanostructure　has　stability　with　a　minimum　energy　of　the　system.　Then　the　Young＇s　moduli　and　strength　of　the　nanostructures　under　tensile　and　compressive　loads　are　predicted,　using　the　molecular　dynamics　(MD)　method.　Finally,　failure　modes　of　the　nanostructures　are　discussed.　It　is　shown　that　the　CNT-based　3D　nanostructures　have　ideal　mechanical　properties,　being　superior　to　those　of　twisted　CNT　bundles.　The　tensile　and　compressive　behaviors　and　failure　modes　of　the　nanostructures　depend　on　the　lengths　of　REs　of　CNTs.　(C)　2014　Elsevier　B.V.　All　rights　reserved.