NOVELTY - Nano-structured manganese spinel comprises tetragonal phase cobalt manganese oxide nano-particles, cubic phase cobalt manganese oxide nano-particles and tetragonal phase cobalt manganese oxide nano-wires (I), magnesium manganese oxide nano-particles, hausmannite nano-particles, zinc manganese oxide hollow nano-spheres, hollow microspheres or nano-sheets. The particle diameter of magnesium manganese oxide or hausmannite nano-particle is 80-200 nm. The diameter of zinc manganese oxide nano-sphere is 400-600 nm. The diameter of zinc manganese oxide hollow microsphere is 2 mu m.    USE - The manganese spinel is useful in the fields of spinel oxide nano-material preparation, metal air battery and fuel battery electric catalysis.    ADVANTAGE - The manganese spinel: has large specific surface area and high electric catalytic efficiency; increases the contact between the activated substance and, oxygen and electrolyte; and can prepare in room temperature, thus consumes less energy.    DETAILED DESCRIPTION - Nano-structured manganese spinel comprises tetragonal phase cobalt manganese oxide nano-particles, cubic phase cobalt manganese oxide nano-particles and tetragonal phase cobalt manganese oxide nano-wires of formula (CoxMn3-xO4) (I), magnesium manganese oxide nano-particles, hausmannite nano-particles, zinc manganese oxide hollow nano-spheres, hollow microspheres or nano-sheets. The particle diameter of (I) nano0-particle is 80-200 nm. The (I) nano-wires with diameter of 10-30 nm and length of 1-2 mu m are interwoven to form a net-shaped structure. The particle diameter of magnesium manganese oxide or hausmannite nano-particle is 80-200 nm. The diameter of zinc manganese oxide nano-sphere is 400-600 nm and the shell is 40 nm thick. The edge length of the zinc manganese oxide hollow nano-cube is 400 nm and the wall is 40 nm thick. The diameter of zinc manganese oxide hollow microsphere is 2 mu m. The edge length of zinc manganese oxide mu m hollow microcube is 2.5 micrometers. The atomic ratio of cobalt to manganese of the tetragonal phase (I) nano-particle is 1:1.72. The atomic ratio of cobalt to manganese of the cubic phase (I) nano-particle is 1:1.11. The atomic ratio of magnesium to manganese of the tetragonal phase (I) nano-particle is 1:2.92. The atomic ratio of the tetragonal phase zinc manganese oxide hollow nano-sphere is 1:1.74. The atomic ratio of zinc to manganese of the tetragonal phase zinc manganese oxide hollow nano-cube is 1:1.49. INDEPENDENT CLAIMS are also included for:    (1) preparing the nano-structured manganese spinel, comprising (i) adding non-crystal hausmannite nano-particle and metal salt into de-ionized water, stirring to completely dissolve the metal salt to obtain the turbid liquid, (ii) adding the reducing agent into the turbid liquid while magnetic stirring, stirring until the bubbles disappear, and (iii) separating to obtain the solid by centrifugation, washing with de-ionized water and anhydrous ethanol for 2-3 times and drying at 80 degrees C at 0.1 MPa for 4 hours; and    (2) application of the nano-structured manganese spinel, comprising forming three-electrode system as alkali electric catalyst to be applied to test the reducing property of the oxygen, where the three-electrode system is formed through taking the nano-material as work electrode, and taking platinum piece as electrode, taking the saturated potassium chloride silver/silver chloride as reference electrode and taking the potassium hydroxide as electrolyte, where the activated substance in the manganese-series composite oxide as work electrode is composed of manganese-series spinel nano-material and activated carbon in a mass ratio of 3:7.