Catalysts prepared from a mixture of Mn3O4 powders and carbon blacks carrying pyrolytic MnO2 were investigated for catalysis of oxygen reduction. It was found that the introduction of Mn3O4 to the pyrolysis process of manganous nitrate carried out on carbon blacks improved the performance of air electrodes as the amount of Mn3O4 was controlled within 15 wt % relative to the weight of carbon carrier. The mechanism of this improved behaviour was also investigated using X-ray diffraction (XRD). The results showed that Mn3O4 induced the formation of favourable MnO2 crystalline grains during the pyrolysis of manganous nitrate. The induced effect and the blocking effect of Mn3O4 on the catalysis of air electrodes catalysed by pyrolytic MnO2 were demonstrated both on carbon black and porous carbon carriers.