The first-principles calculations were used to investigate the oxygen evolution reaction (OER) on the (100) surface of the spinel Co3O4, a high-performance oxidation catalyst. We compared the OER activities by the free-energy changes on three different covered surfaces including (i) clean, (ii) 0.5 monolayer O covered, and (iii) 0.5 monolayer OH covered surfaces, and the computed overpotential (eta) for the three surfaces followed the order: O covered (eta = 0.45 V) < OH covered (0.93 V) < clean (1.82 V). Furthermore, the influence of activities was analyzed by Bader charge, which showed that the Co Bader charge on the O/OH covered (100) surface was more than that on the clean surface. Based the above analysis, the O-containing species covered Co3O4 (100) surface exhibited better OER catalytic performance than that of the clean surface in the OER cycle. [GRAPHICS] .