The design of highly efficient, robust and earth-abundant electrocatalysts for oxygen evolution reaction (OER) is a prodigious challenge for the rapid growth of global energy demand. Herein, an active catalyst composed of porous graphene and cobalt oxide (PGE-CoO) has been synthesized, demonstrating high porosity, large specific surface area and fast charge transport kinetics. The catalyst also exhibits excellent electrochemical performance towards OER with a low onset potential and high catalytic current density. The enhanced catalytic activity could be ascribed to porous structure, high electroactive surface area and strong chemical coupling between graphene and CoO nanoparticles. Moreover, this OER catalyst also shows good stability in the alkaline solution. The high performance and strong durability suggest that the porous structured composite is favorable and promising for water splitting.