Multi-walled　carbon　nanotubes　bearing　hydroxyl　group　were　modified　with　toluene　diisocyanate　(TDI)　and　stabilized　with　caprolactam.　The　functionalized　carbon　nanotubes　were　used　to　prepare　monomer　casting　polyamide　6(MC　nylon　6)/carbon　nanotubes　nanocomposites.　The　results　of　FTIR　proved　that　isocynate　groups　have　been　incorporated　into　carbon　nanotubes　successfully.　XRD　results　showed　that　the　addition　of　the　functionalized　carbon　nanotubes　has　no　significant　influence　on　the　crystal　structure　of　MC　nylon　6,　whereas　the　untreated　carbon　nanotubes　could　hinder　the　growth　of　alpha(2)-crystal　of　nylon　6;　with　the　loading　of　0.3　Wt%　of　the　functionalized　carbon　nanotubes,　the　crystallinity　degree　of　the　nanocomposites　is　almost　equal　to　that　of　pure　MC　nylon　6,　whereas　as　the　loading　increased　to　0.5　Wt%,　the　crystallinity　degree　of　MC　nylon　6　decreased.　DSC　revealed　that　carbon　nanotubes　in　MC　nylon　6　acted　as　effective　nucleation　agents.　The　peak　temperature　of　crystallization　for　MC　nylon　6　increased　by　10　degrees　C　from　173.4　to　183.5　degrees　C,　and　the　temperature　range　of　crystallization　decreased,　indicating　that　the　carbon　nanotubes　act　as　heterogeneous　nucleation　agents　for　MC　nylon　6.