NOVELTY - Preparing platinum/aluminum oxide fiber composite catalyst, comprises: e.g. dissolving chloroplatinic acid and sodium hydroxide in water and separating out disodium hexahydroxy platinate (IV) and dihydrogen hexahydroxy platinate (IV); dissolving both the solutions in the water, adding diacetone, methanol and formic acid drop wise to obtain a nanometer platinum particle black solution (A) and adding an organic complexing agent to obtain black nanometer platinum particle solution (B); and soaking aluminum oxide fiber cotton to the solutions (A) and (B) and igniting it to obtain the product.    USE - The platinum/aluminum oxide fiber composite catalyst is useful for methanol low-temperature combustion.    ADVANTAGE - The platinum nanometer particles generated are uniform and mono-dispersible. The platinum/aluminum oxide fiber catalyst has a high catalytic activity for methanol low-temperature catalytic combustion. The device used in the synthesizing process is simple. The method has high preparation efficiency, does not use hydrogen gas as the reducing agent and can be used for large-sca1e preparations.    DETAILED DESCRIPTION - Preparing platinum/aluminum oxide fiber composite catalyst for methanol low-temperature combustion, comprises: (i) dissolving chloroplatinic acid and sodium hydroxide in water, where the mass ratio is 1:(0.5-1.5), refluxing the mixture for 36 hours along with agitating, separating out a brownish-yellow precipitate, filtering, washing the yellow precipitate with de-ionized water and drying it to obtain disodium hexahydroxy platinate (IV); regulating the pH of the filtrate to be less than 6, separating out a cream-yellow precipitate, filtering, washing it with de-ionized water and drying to obtain dihydrogen hexahydroxy platinate (IV); (ii) dissolving the disodium hexahydroxy platinate (IV) or dihydrogen hexahydroxy platinate (IV) in the water to obtain a brownish-yellow muddy solution, adding diacetone to the solution, where the molar ratio of disodium hexahydroxy platinate (IV) or dihydrogen hexahydroxy platinate (IV) to the diacetone is 1.5-10, heating the mixture and refluxing it, adding methanol solution drop wise, where the molar ratio of the disodium hexahydroxy platinate (IV) or dihydrogen hexahydroxy platinate (IV) to the methanol is 1:525; adding formic acid solution drop wise, where the molar ratio of the disodium hexahydroxy platinate (IV) or dihydrogen hexahydroxy platinate (IV) to the formic acid is 1:1-4; reacting the mixture until the color of the reaction system turns to grey green from brownish-red and later turns to black; cooling the mixture to room temperature, extracting with methylbenzene, filtering the water layer to obtain a nanometer platinum particle black solution (A); adding an organic complexing agent diacetone, where the molar ratio of the nanometer platinum particle to the diacetone is 1:(4-12); heating the mixture to 85 degrees C and reacting for 24-72 hours under agitating conditions, extracting with methylbenzene, filtering the water layer to obtain black nanometer platinum particle solution (B); and (iii) soaking aluminum oxide fiber cotton to the solutions (A) and (B) after diluting the solutions with methanol (15-30 times), where the mass ratio of the platinum to the aluminum oxide fiber cotton is 1:500-1000; taking out the fiber cotton and igniting it to obtain the platinum/aluminum oxide fiber composite catalyst after the solvent volatilizes.