NOVELTY - Preparation of perfluorinated sulfonic acid composite proton exchange membrane includes dissolving dried perfluorinated sulfonic acid resin in high-boiling-point polar solvent; heating and dissolving; ultrasonically treating the solution to remove bubbles and impurities; adding half volume of the solution to a glass board with a groove; dipping polypropylene (PP) diaphragm in the solution; and after forming film, drying to obtain composite proton exchange membrane with perfluorinated sulfonic diaphragm on one face.    USE - Preparation of perfluorinated sulfonic acid composite proton exchange membrane (claimed) useful for vanadium redox battery.    ADVANTAGE - The composite membrane has good vanadium resistance, good proton conduction property, good mechanical performance, and good chemical stability; and provides good performance for single vanadium redox battery. The method is simple and easy to implement, easy for industrial production, and environment friendly; and has low cost.    DETAILED DESCRIPTION - Preparation of perfluorinated sulfonic acid composite proton exchange membrane comprises:    (A) dissolving dried perfluorinated sulfonic acid resin in high-boiling-point polar solvent; and heating and dissolving in a reaction kettle to prepare 2-40 mass% solution;    (B) ultrasonically treating the solution to remove bubbles and impurities;    (C) adding half volume of the solution to a glass board with a groove; dipping PP diaphragm in the solution at 30-120 degrees C for 1-12 hours; after forming film by casting method, pasting method, or gum dipping method, drying to obtain composite proton exchange membrane with perfluorinated sulfonic diaphragm on one face; and    (D) adding the rest amount of the solution of step (B) to the surface of proton exchange membrane in step (C); and after forming film by casting method, pasting method, or gum dipping method, drying to remove the film in deionized water and obtain double-face perfluorinated sulfonic acid composite proton exchange membrane.