The cobalt oxide and carbon nanotubes (Co3O4/CNTs) nanocomposites are successfully synthesized using hydrothermal method. The as-synthesized nanocomposite materials are utilized in the electrophoretic deposition (EPD) to fabricate the electrodes, whose electrochemical properties are investigated in a three-electrode configuration cell with 1 M KOH electrolyte. By adjusting the precursor concentration, reaction time in hydrothermal process, and annealing temperature, the optimum conditions are obtained. From the experimental results, when the cobalt nitrate concentration is taken as 2 mmol, reaction time is 8 h, and the temperature is maintained at 180 °C in the hydrothermal process, the synthesized Co3O4/CNTs nanocomposites shows the highest specific capacitance of 705 F g−1 at a charging current of 3 A g−1. Besides, the binder-free electrode preparation through EPD has effectively reduced the inner resistance of the electrode and makes the cycle stability excellent.