This work reports the preparation of N-doped reduced graphene oxide decorated NiSe2 nanoparticles (N-rGO/NiSe2) in the presence of different amount of graphene oxide reactant by a simple two-step process, which contains hydrothermal preparation of Ni(OH)(2) precursor and then solvothermal synthesis of N-rGO/NiSe2 composites with different content of N-rGO. The as-prepared N-rGO/NiSe2 composites is characterized by power X-ray diffraction, Raman spectroscopy, high-resolution X-ray photoelectron spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy and N-2 adsorption -desorption isotherm. The results show that N-rGO acts as supporter of NiSe2 nanoparticles to prevent them from aggregation, leading to the increase in specific surface area and electrical conductivity of material. The optimized N-rGO/NiSe2 composite can deliver high specific capacitance of 2451.4 F g(-1) at a current density of 1 A g(-1). Using activated carbon (AC) as negative electrode and the optimized N-rGO/NiSe2 composite as positive electrode, an asymmetric supercapacitor is constructed. This fabricated asymmetric supercapacitor can work stably under the potential window of 0-1.6 V, and presents the maximum energy density of 40.5 Wh kg(-1) at a power density of 841.5 W kg(-1). Moreover, the N-rGO/NiSe2//AC asymmetric supercapacitor exhibits good cyclic stability.