The invention discloses a CoO/Co/C ternary composite material. A preparation method thereof comprises the following steps: taking oleylamine and cobalt acetylacetonate as main raw materials, heating under a protective atmosphere after uniformly mixing the two raw materials for reaction; continuously warming an obtained product, carrying out a second heat preservation reaction to obtain a mixed liquor of CoO particles and oleylamine, and then directly roasting the obtained mixed liquor under the protective atmosphere so as to obtain the CoO/Co/C ternary composite material. The referred raw materials are cheap and easy to get, and poisonous and harmful organic surface active agents and additives do not need to be used additionally, so that the composite material is safe and environmentally-friendly; the preparation technology is simple and environmentally-friendly, the reaction conditions are mild, the preparation technology can be effectively simplified, and the cost is reduced; and the obtained CoO/Co/C ternary composite material is applied to oxygen reduction reactions, and can be excellent in electro-catalytic property.