In order to ameliorate the capacitance and energy density of supercapacitors in aqueous electrolytes, nitrogen- and phosphorus-codoped carbon microspheres/reduced graphene oxide nanocomposites are obtained by hydrothermal treatment of graphite oxide and N,P-doped carbon microsphere. The as-prepared nanocomposites display a high specific surface area of 604.3 m(2) g(-1) and hierarchical pore structure composed of micropores, mesopores, and macropores. N,P-codoped carbon microspheres/reduced graphene oxide are used as electrode materials in the redox electrolyte of H2SO4 and KI aqueous solution, exhibiting a excellent capacitance performance of up to similar to 654 F g(-1) at 2 A g(-1), corresponding to the energy density of 14.53 Wh kg(-1) at power density of 402 W kg(-1). Even at a high current of 20 A g(-1), the electrode can keep a capacitance of 318 F g(-1), showing an energy density of 7 Wh kg(-1) at power density of 3984 W kg(-1). This study indicates the potential of nitrogen- and phosphorus-codoped carbon microspheres/reduced graphene oxide in high energy density supercapacitor.