NOVELTY - Preparing platinum-based catalyst, comprises: e.g. adding metal salt precursor of tetrahydrated hexanitro platinic acid, sodium citrate or sodium oxalate and alcohol reductant in organic solvent, adding sodium hydroxide in the mixed solution, adding carbon support in the mixed solution, stirring the solution at room temperature to uniformly distribute metal-solution grains on the carbon support, adding the solutions to oxalic acid and filtering, water washing the filter cake and cooling and grinding the filter cake.    USE - The method is useful for preparing a platinum-based catalyst for a fuel cell (claimed).    DETAILED DESCRIPTION - Preparing a platinum-based catalyst for a fuel cell comprises: adding metal salt precursor of tetrahydrated hexanitro platinic acid, sodium citrate or sodium oxalate and alcohol reductant in organic solvent, and stirring the mixed solution at room temperature for 20-40 minutes, where volume concentration of the metal salt precursor is 5-25 g/L, the volume ratio of alcohol reductant and organic solvent is 1:5-1:2 and the mass ratio of the metal salt precursor and the complexing agent is 1-7:3-1; adding the sodium hydroxide in the mixed solution to regulate pH value to 9-13; mixing the carbon support including compound of granulous carbon black and linear carbon nanotube composite in a container and then adding isopropanol and water, ultrasonically dispersing the mixture and then suction filtering the mixture to obtain a filter cake, drying the filter cake and then pryogenic decomposing the filter cake at 300-600 degrees C under the protection of inert gas to obtain polyelement composite carbon support, and adding the obtained carbon support in the mixed solution, stirring the solution at room temperature, and uniformly distributing metal-sol grains on the carbon support, where the molar ratio of the platinum to carbon is 0.02-0.1:1 and the mass ratio of the granulous carbon black and linear carbon nanotube is 1:3-5; adding the solutions to oxalic acid to regulate pH value to 1-5; suction filtering the mixed solution, washing the filter cake using water until nitrate ion is undetectable, then vacuum drying the filter cake, and cooling and grinding the filter cake.