Nanostructured manganese dioxide (MnO2)/reduced graphene oxide (RGO) composite is fabricated via a simple hydrothermal process. The MnO2/RGO composite is used to construct supercapacitors as electrodes with high loading mass of active materials. The electrochemical properties of constructed supercapacitors are tested by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. Electrochemical measurements demonstrate that MnO2/RGO electrode exhibits a high specific capacity of 316 F·g−1 at a current density of 200 mA·g−1 and good long-term cycling stability with capacitance retention of 93% at 500 mA·g−1 after 1000 cycles. The superior electrochemical performance of as-prepared composite could be mainly attributed to its unique structure, which is composed of MnO2 nanoflakes well-integrated on the surfaces of RGO.