In this study, effects of graphene content on the rheological behavior and viscous activation energy of graphene/nylon 6 composites were investigated. Twin-screw extruder was used to produce 10wt% graphene/nylon 6 master batch. The banbury mixer was used for dilution process to provide another 3wt% and 5wt%. Differential scanning calorimetry (DSC) and Polar light microscopy (PLM) were used to study the crystalline morphology, graphene dispersion and thermal properties. The rheological properties and viscous activation energy of graphene/nylon 6 composites were studied by rheometer under different temperatures and shear rates. The DSC and PLM results showed that 5℃ melting temperature increased by adding graphene and good dispersion of graphene in the nylon 6 matrix. The viscosities of graphene/nylon 6 composites increased with increasing graphene concentration. The interaction between nylon and graphene which results in a strong restriction of movement in nylon 6 molecule was revealed. As the concentration of graphene increased, the flow behavior index (n) decreased from 0.99 to 0.51, indicated the flow behavior changed from newtonian to pusedoplastic flow. The viscosities of graphene/nylon 6 composites were sensitive to temperature. The viscous activation energy of composites decreases as the concentration of graphene increases.