In this paper, MnO2/reduced graphene oxide (rGO) composite is prepared by one-step hydrothermal method. With anchoring MnO2 nanosheets on the surface of rGO, the extraordinary structure provides MnO2/rGO composite with large specific surface area and numerous channels for rapid diffusion of electrolyte ions, electron transport and high conductivity due to the presence of rGO. Electrochemical results demonstrate that MnO2/rGO composite has good capacitive performance with a specific capacitance of 255 F.g(-1) at a current density of 0.5 A.g(-1), a retention rate of 84.5% after 10,000 cycles at 10 A.g(-1), and an energy density of 33.33 Wh.kg(-1) with a power density of 20,000 W.kg(-1). The results above indicate that MnO2/rGO composite has potential applications for supercapacitor electrode materials.