It is a great challenge to develop Co3O4-based electrocatalysts of excellent performance for oxygen evolution reaction, because of its poor electrical conductivity. In this paper, we have prepared pristine Co3O4 (P-Co3O4) and Co3O4-C polyhedrons via two different calcination strategies. Then we have also displayed a simple and green reduction method to synthesize reduced Co3O4 (R-Co3O4) polyhedron with abundant surface oxygen vacancies. Oxygen vacancies and the doping of carbon species can enhance conductivity of electrocatalysts, thus, improving their electrocatalytic activities obviously. R-Co3O4 and Co3O4-C polyhedrons show lower overpotentials of 380 and 420 mV, respectively, compared to P-Co3O4 polyhedron (520 mV) at the current density of 10 mA cm(-2) in 1 M KOH solution (pH 13.7). And they also have smaller Tafel slopes of 86 and 78 mV dec(-1) than that of P-Co3O4 polyhedron (93 mV dec(-1)), respectively. The integrated strategy reported here provides the way to design high-performance electrocatalysts for water oxidation.