NOVELTY - A bacterial proton exchange membrane comprises boron carbide-Nafion (RTM: sulfonated tetrafluoroethylene based fluoropolymer-copolymer)-boron carbide structure or Nafion (RTM: sulfonated tetrafluoroethylene based fluoropolymer-copolymer)-BC-Nafion (RTM: sulfonated tetrafluoroethylene based fluoropolymer-copolymer) structure.    USE - Bacterial proton exchange membrane for hydrogen-oxygen fuel cell (fuel is methanol or liquid in fuel cell) (claimed).    ADVANTAGE - The membrane has low methanol permeability and high proton conductivity and thermal stability. Methanol fuel cell has good application prospect. The method is simple and easy, and has little pollution to environment.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparing the proton exchange membrane which comprises (A) washing bacterial cellulose membrane by deionized water, removing residual culture medium and impurity, and treating at 70-100 degrees C with 0.1-5% alkaline solution for 0.5-4 hours to obtain white and transparent bacterial cellulose film; (B) washing with acid solution and deionized water, boiling, in deionized water 1-3% Nafion (RTM: sulfonated tetrafluoroethylene based fluoropolymer-copolymer) for 5-2 hours, using de-ionized water to wash until bacteria cellulose film pH value is neutral, and obtaining bacterial cellulose gel film; (C) boiling Nafion (RTM: sulfonated tetrafluoroethylene based fluoropolymer-copolymer) for 1 hour with hydrogen peroxide and deionized water, and 3%/ dilute sulfuric acid and deionized water, and processing to obtain film; (D) cutting treated Nafion (RTM: sulfonated tetrafluoroethylene based fluoropolymer-copolymer) film cut into shape, drying and film forming to obtain composite film, stacking treated film and gel-like bacterial cellulose film and treated film, drying and film forming to obtain bacterial cellulose-sandwich composite film, or gel-like bacterial cellulose film after drying to obtain bacterial cellulose dry film, and at 90-110 degrees C for 10-30 minutes, and repeating step of soaking and drying for 1-9 times, to obtain Nafion-BC-Nafion structure of bacterial cellulose -Nafion sandwich composite film; and (E) treating obtained sandwich composite film at 110-130 degrees C for 1-2 hours to obtain the product.