Electroactive materials with excellent performance are developed to be applied in different fields. In this study, Graphene Oxide (GO) was synthesized using the Hummer method then reduced and modified with Cu trough gamma irradiation (radiolytic reduction) for dose variations. The optimum dose that produces the highest electroactive is 35 kGy which was tested with cyclic voltammetry. The results of FTIR analysis show the characteristics of functional groups found in GO and rGO are different. The modification of rGO with Cu was successfully shown from the results of XRD and SEM-EDX analysis. The results of the XRD analysis showed that there are two peaks at position 2 theta 10.58° which showed the presence of GO and at position 2 theta 42.55° which indicates the presence of Cu. The results of the SEM-EDX analysis showed that there is 2.25% wt of Cu on the surface of the rGO.