A flexible electrode of nickel diselenide/carbon fiber cloth (NiSe2/CFC) is fabricated at room temperature by a simple and efficient electrodeposition method. Owing to NiSe2 character of nanostructure and high conductivity, the as-synthesized electrodes possess perfect pseudocapacitive property with high specific capacitance and excellent rate capability. In three-electrode system, the electrode specific capacitance of the NiSe2/CFC electrode varies from 1058 F g–1 to 996.3 F g–1 at 2 A g–1 to 10 A g–1 respectively, which shows great rate capability. Moreover, the NiSe2 electrode is assembled with an active carbon (AC) electrode to form an asymmetric supercapacitor with an extended potential window of 1.6 V. The asymmetric supercapacitor possesses an excellent energy density 32.7 Wh kg–1 with a power density 800 W kg–1 at the current density of 1 A g–1. The nanosheet array on carbon fiber cloth with high flexibility, specific capacitance and rate capacitance render the NiSe2 to be regarded as the promising material for the high performance superconductor.