A facile approach which is based on the different functionalities in graphene focused on facilitating polyamide 6 (PA6) to graft onto graphene surface to form homogeneous nanocomposite in which graphene was well-distributed, leading to increasing physico-mechanical properties of the composite. Graphene was oxidized to form graphene oxide (GO), which was then reacted with amine compounds to obtain the graphene bonding with amine functional groups of –NH₂ and –(CH₂)₆NH₂. The nanocomposite of functionalized graphene grafted by PA6 was fabricated by in situ polycondensation of caprolactam (CPL) and connection of the PA6 to the functionalized graphene, and their continuous nanocomposite fibers were prepared by use of melt spinning and drawing process. The grafting PA6 chains on graphene sheets were confirmed by FTIR, TGA and AFM measurements. Replacement of the –COOH group by –NH₂ and –(CH₂)₆NH₂ in the composite of PA6 and graphene changed the grafting polymerization chemistry, thereby leading to the covalent attachment of longer graft polymer chains to the graphene. Tensile strength of the nanocomposite fibers containing the –(CH₂)₆NH₂ functional group with 0.1 wt% graphene loading was significantly increased, over twice as high as that of neat PA6.