In this study, a highly active oxygen reduction reaction (ORR) electrocatalyst (MG-15) of Mn3O4 nanopartides (NPs) supported by reduced graphene oxide (rGO) has been fabricated through one-step microwave-assisted synthetic route. Upon microwave-assisted synthesis, the formation of Mn3O4 NPs and the reduction of GO occurs simultaneously. Transmission electron microscope (TEM) profile reveals that Mn3O4 NPs are uniformly distributed evenly on the winkled rGO sheets. The MG-15 hybrid materials show enhanced electrocatalytic activity compared to rGO, Mn3O4 NPs and the mixture of rGO and Mn3O4 NPs, which indicates that the synergistic effect of Mn3O4 and rGO enhances the overall performance. Additional, the oxygen reduction peak of the MG-15 catalyst in a 0.1 M KOH solution is tested at -0.15 V, which is more positive than Pt/C (-0.154 V). The onset potential of the MG-15 is close to Pt/C. Most importantly, the mechanism analysis shows that it favors the 4e(-) pathway for ORR. Furthermore, the MG-15 also exhibit excellent durability and methanol. (C) 2016 Elsevier Inc. All rights reserved.