NOVELTY - Preparing carbon-supported Pt-Au bimetal nano electro-catalyst with high stability comprises: (a) mixing the carbon-supported platinum catalyst and water; and (b) dropping in monohydric alcohol, dihydric alcohol or trihydric alcohol.    USE - The method is useful for preparing carbon-supported Pt-Au bimetal nano electro-catalyst with high stability (claimed). The catalyst is also useful as the cathode catalyst of proton exchange membrane fuel cells.    ADVANTAGE - The invention is simple and suitable for mass production.    DETAILED DESCRIPTION - Preparing carbon-supported Pt-Au bimetal nano electro-catalyst with high stability comprises method 1: (a) mixing the carbon-supported platinum catalyst and water to evenness, at negative 10-10 degrees C, adding the aqueous solution of chloroauric acid into the carbon-supported platinum catalyst for mixing and milling the chloroauric acid solution and Pt/C catalyst to evenness, and controlling an atomic ratio of Pt to Au as 18:1-5:1; (b) dropping in monohydric alcohol, dihydric alcohol or trihydric alcohol in (a), milling at negative 10-10 degrees C for the adequate reaction, pumping, filtering, washing by water, and drying in vacuum for preparing the carbon-supported Pt-Au bimetal nano electro-catalyst; and method 2: (a) mixing the carbon-supported platinum catalyst and water to evenness, at negative 10-10 degrees C, adding the aqueous solution of chloroauric acid into the carbon-supported Platinum catalyst for mixing and milling the chloroauric acid solution and Pt/C catalyst to evenness, and controlling an atomic ratio of Pt to Au as 18:1-5:1; (b) dropping in monohydric alcohol, dihydric alcohol or trihydric alcohol in (a), milling at negative 10-10 degrees C for the adequate reaction, pumping, filtering, washing by water, and drying in vacuum for preparing the carbon-supported Pt-Au bimetal nano electro-catalyst; and (c) processing the catalyst prepared in (b) for 0.5-4 hours at a high temperature from 100-700 degrees C in a inert atmosphere or reducing atmosphere so as to prepare the heat-treated Pt-Au/C bimetal nano electro-catalyst with different grain sizes.