In this paper, hierarchically porous MgMn.sub.2O.sub.4 microspheres, which assembled with average size of about 30 nm nanosheets, have been synthesized by a facile solvothermal process followed by calcination method. The electrocatalytic properties of the products towords oxygen reduction reaction (ORR) are further investigated. Benefitting from its unique structural characteristics, the hierarchically porous MgMn.sub.2O.sub.4 microspheres exhibit more positive onset potential and enhanced current density than the MgMn.sub.2O.sub.4 blocks and irregular sheets, and their ORR catalytic performance is better than the pure manganese oxide (Mn.sub.2O.sub.3) which is prepared through the same method. In addition, the MgMn.sub.2O.sub.4 microspheres own superior durability and methanol tolerance than that of Pt/C catalysts in spite of slight negative onset potential, which can be a promising non-noble metal ORR catalyst.