Ni(OH)2/AC/CNT composite has been prepared via a green rapid microwave assisted method in an ethylene glycol medium. Scanning electron microscopy images show that Ni(OH)2 nanoparticles, activated carbon spheres and nanotubes constructed a three-dimensional (3-D) connected network, which lead to a high specific capacitance 1038Fg−1 at current density of 1Ag−1. Based on Ni(OH)2/AC/CNT composite as positive electrode material and activated carbon as negative electrode material, an asymmetric supercapacitor of AC//Ni(OH)2/AC/CNT was fabricated. The unit supercapacitor demonstrates excellent electrochemical performances using non-woven fabric as separator and 6M KOH as electrolyte within 1.6V operation window. The maximum specific capacitance of 82.1Fg−1 is achieved at 0.5Ag−1 and the energy density can reach up to 32.3Whkg−1 at power density of 504.8Wkg−1. Furthermore, 83.5% capacitance retention is obtained after 1000 charge-discharge cycles. These results indicate that the AC//Ni(OH)2/AC/CNT supercapacitor is promising to be applied in a practical device for energy storage devices.