Cubic Co3O4 and CoO nanopowders were obtained by annealing Co(OH)2 precursor prepared from facile liquid phase precipitation method under air or hydrogen atmosphere. Compared with CoO, Co3O4 nanopowders possess larger size, bigger specific surface area, average pore size and pore volume. The electrochemical results show that Co3O4 delivers higher specific capacitances because of its high electrochemical activity, Co3O4 and CoO could achieve 618 F/g and 147 F/g at 0.5 A/g, respectively. However, CoO displays better rate performance, and the capacitance retention at 10 A/g compared with 0.5 A/g is 49.0% higher than 37.9% of Co3O4. After 2000 cycle tests, the capacitance of Co3O4 and CoO could achieve 100% and 137% of their initial capacitances, implying their excellent cycle performances.