NOVELTY - Manganese oxide catalyst loaded with platinum nanoparticle comprises manganese oxide carrier and platinum nanoparticle loaded on the surface of manganese oxide carrier. The load of the platinum nanoparticle accounts for 0.1-10% the mass of the catalyst.    USE - The catalyst is useful for catalytic degradation of formaldehyde as indoor pollutant at 20-80 degrees C; and preparing electrode material of battery, magnetic materials and fuel cell (all claimed).    ADVANTAGE - The catalyst can completely catalyze and degrade formaldehyde at low temperature, and has high efficiency, low energy consumption, simple and convenient operation, mild reaction condition and no secondary pollution.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for preparing manganese oxide catalyst loaded with platinum nanoparticle, comprising: (a) adding sodium citrate and polyvinyl pyrrolidone into a container, then mixing with water to get mixed solution, stirring the solution to dissolve, introducing the container in a water bath of 60-100 degrees C, maintaining stirring state, adding chloroplatinic acid aqueous solution drop wise into the obtained mixed solution, continuously stirring, where the molar ratio of sodium citrate to chloroplatinic acid in the mixed solution is (10:1)-(30:1) and the molar ratio of polyvinyl pyrrolidone to chloroplatinic acid is (10:1)-(70:1), dripping aqueous solution containing ascorbic acid, where the molar ratio of ascorbic acid to chloroplatinic acid is (10:1)-(30:1), continuously stirring, and reacting at 60-100 degrees C to obtain the aqueous solution containing platinum nanoparticle; and (b) ultrasonic dispersing of manganese oxide carrier in water, adding the aqueous solution containing platinum nanoparticle prepared in step (a), introducing the container into water bath of 60-100 degrees C to react for 1-8 hours, suction filtering the prepared solution for separating, washing the filtered solid with water, then washing it with ethanol, and drying to obtain manganese oxide catalyst loaded with platinum nanoparticle.