NOVELTY - Preparation of fuel cell compound proton exchange membrane enhanced by silicon dioxide (SiO2) three-dimensional ultra-thin membrane, comprises: (a) preparing epoxy resin micro filtering membrane; (b) preparing three-dimensional SiO2 ultra-thin membrane; and (c) preparing compound proton exchange membrane enhanced by SiO2 ultra-thin membrane.    USE - The process is useful for preparing fuel cell compound proton exchange membrane enhanced by silicon dioxide three-dimensional ultra-thin membrane (claimed).    ADVANTAGE - In utilizing the process, the prepared fuel cell compound proton exchange membrane has high moisture holding capability, high-temperature resistance, and cell work efficiency at high temperature.    DETAILED DESCRIPTION - Preparation of fuel cell compound proton exchange membrane enhanced by silicon dioxide (SiO2) three-dimensional ultra-thin membrane, comprises: (a) preparing epoxy resin micro filtering membrane: completely dissolving the epoxy resin and the amine in the polyethylene glycol medium by the weight ratio of 1:1 to 10:1; where the weight ratio of the polyethylene glycol and the epoxy resin is 1:1 to 10:1; and obtaining the clarified solution, and removing the bubble, and casting and keeping temperature for more than 4 hours at 35-85 degrees C; continuously increasing the monomer solution viscosity and producing the phase separation while polymerizing; curing the gel into the white epoxy resin nascent state membrane; immersing the nascent state membrane into the water; removing the medium polyethylene glycol; and obtaining the epoxy resin micro filtering membrane; (b) preparing three-dimensional SiO2 ultra-thin membrane: soaking the epoxy resin micro filtering membrane with the three-dimensional frame structure in (a) into tetraethoxysilane for 1-5 hours, and exposing for 10-20 hours in aqueous ammonia atmosphere at 30-60 degrees C; and performing the in situ hydrolysis to the tetraethoxysilane in the template pore channel of the epoxy resin micro filtering membrane, depositing the generated SiO2 on the surface of the template pore channel; forming the compound membrane of the three-dimensional SiO2 continuous phase coating epoxy resin; drying for 1-5 hours to remove the generated ethanol and the absorbed ammonia water; increasing temperature of the muffle furnace to 600-900 degrees C and keeping for 10-60 minutes; calcining at high temperature; removing the epoxy resin; sintering and shaping the SiO2; and forming the three-dimensional SiO2 ultra-thin membrane by the SiO2 coated on the surface of the epoxy resin; and (c) preparing compound proton exchange membrane enhanced by SiO2 ultra-thin membrane: casting the perfluorinated sulfonic resin solution with a certain amount on the SiO2 micro pore membrane prepared in (b), and adopting the alcohol solvent solution for the perfluorinated sulfonic resin solution with concentration of 3-10%, and heating for 1-24 hours at 30-120 degrees C; volatilizing the solvent; heating for 5 minutes to 5 hours at 120-200 degrees C under the vacuum atmosphere; protonizing, and obtaining the compound proton exchange membrane enhanced by SiO2 ultra-thin micro pore membrane after washing by deionized water.