NiO was successfully loaded on hydrothermally treated mesocarbon microbeads (h-MCMB) to form NiO/h-MCMB composites by thermal decomposition of the precursor via a co-precipitation process in ethanol-water system. XRD, IR, SEM and HRTEM tests were applied to investigate the structure, morphology and the formation mechanism of the NiO/h-MCMB composites. Electrochemical characteristics of the composites were examined by cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) techniques in a three-electrode configuration with 1 M KOH solution. Electrochemical tests demonstrated that unsupported NiO with 5-10 mn grain sizes and higher specific area enlarged the contact area, made the best electroactive material and enhanced electrochemical reaction rate. Moreover, h-MCMB as support further increased the conductivity of the material, promoted the dispersion and utilization of NiO considerably, improved the electrochemical stability and power property of composite electrode. Specific capacitance of ca. 637 F g(-1) (C-NiO) could be delivered at 6 mA cm(-2) for the NiO/h-MCMB composite with 23 wt.% NiO loading. (C) 2007 Elsevier B.V. All rights reserved.