NOVELTY - Preparation of multilayer perfluorinated sulfonic acid ion-exchange membrane by solution casting method involves putting a weighed quantity of perfluoro type fluorine-sulfonic acid resin into 10-30% sodium hydroxide solution, transforming at 100 degrees C for 15-24 hours in the oven to give sodium-type perfluorinated sulfonic resin; taking hydrochloric acid solution (5-30 wt.%), putting the sodium-type membrane in it, transforming for 5-10 hours; taken out the transformed membrane, and cleaning till it is neutral, adding ethanol (1%) and water (20%) in the solution.    USE - For preparation of multilayer perfluorinated sulfonic acid ion-exchange membrane by solution casting method (claimed).    ADVANTAGE - The method features in the casting cast by a layer type solution, making the thickness of the film can reach 200 mu m, overcomes the disadvantages of the traditional casting to produce a thinner. The method can make perfluorinated sulfonic acid resin to preserve the long-chain structure, making the membrane made of perfluorinated sulfonic acid to maintain the original proton conductivity, heat resistance, electrochemical properties and chemical stability; has high degree of automation, the operation is simple, it can realize large scale continuous production, and process controllability is high, and the product quality is stable.    DETAILED DESCRIPTION - Preparation of multilayer perfluorinated sulfonic acid ion-exchange membrane by solution casting method involves transforming sodium fluoride: putting a weighed quantity of the perfluoro type fluorine-sulfonic acid resin into 10-30% sodium hydroxide solution, transforming at 100 degrees C for 15-24 hours in the oven to give sodium-type perfluorinated sulfonic resin; cleaning the well, take out sodium-type perfluorinated sulfonic resin from the oven, the resin and sodium hydroxide solution separated by gauze, pouring the sodium hydroxide solution into a bottle; cleaning the resin till it is neutral, testing the pH value with pH test paper, which is sodium-type; dissolving water and the isopropyl alcohol solution and cleaning till it is neutral, drying the resin at 250 degrees C, the rotating speed is set to be 120 revolutions/minute; after temperature reaches 250 degrees C, the pressure is stable at 10 MPa; using constant temperature and pressure, to dissolve for 3-6 hours, closing the reaction kettle, reducing the temperature, taking out solution; using high boiling point solution to replace the following steps: taking out the solution in a container, adding water from a certain amount of high boiling point solvent; then put into the container at 140 degrees C in the oven, drying the solution (concentration is 15-30%); flow along the upper surface to obtain the solution into 3 parts of part of a casting film-forming on the machine; the first time, temperature is 140 degrees C, the rotating speed is 0.1-3 m/minutes, the thickness is 0.20-0.5 mm, the width is 0.3-1 mm; complete flow baking for 10-60 minutes at 140 degrees C, and flowing the second time, the second time temperature is 140 degrees C, the rotating speed is 0.0.1-3 m/minutes, the knife edge thickness is 0.2-0.5 cm, knife edge width is 0.3-1 mm; complete flow baking for 10-60 minutes at 140 degrees C, and flowing the third time, the third time temperature is 140 degrees C, the rotating speed is 0.1-3 m/minutes, the knife edge thickness is 0.2-0.5 mm, knife edge width is 0.3-1 mm; complete flow baking at 140 degrees C for 1-3 hours; uncovering the film; transformation (membrane type sodium hydrogen into a film): taking hydrochloric acid solution (5-30 wt.%), putting the sodium-type membrane in it, transforming for 5-10 hours; taken out the transformed membrane, and cleaning till it is neutral, adding ethanol (1%) and water (20%) in the solution.