NOVELTY - Producing hydrogen decomposing photo-electro-catalytic film comprises e.g. taking sodium acetate cellulose or sodium carboxymethyl cellulose and polyethylene pyrrolidone, mixing in a beaker, dissolving in distilled water, heating, casting on flat glass plate, placing in oven and drying, heavy metal ions crosslinking, soaking in a solution containing anionic group, drying, obtaining anode film, preparing bismuth oxyhalide film, mixing and dispersing chitosan or polyimide and polyvinylpyrrolidone in beaker, adding acetic acid aqueous solution, stirring, preparing cathode film, and drying.    USE - The method is useful for producing hydrogen decomposing photo-electro-catalytic film (claimed).    ADVANTAGE - The film can generate photo electric hole separation, and has high hydrogen production quantum efficiency of 90-96% and high hydrogen purity of 99-99.9%. The method saves energy consumption by 15-40%.    DETAILED DESCRIPTION - Producing hydrogen decomposing photo-electro-catalytic film, comprises (i) taking 2-10 g sodium acetate cellulose or sodium carboxymethyl cellulose and 3-10 g polyethylene pyrrolidone, mixing in a beaker, dissolving in distilled water, heating and stirring, casting on the flat glass plate, placing in an oven and drying at 20-50 degrees C, heavy metal ions crosslinking for 5-30 minutes, soaking in a solution containing anionic group for 5-30 minutes, room temperature drying, obtaining anode film with thickness of 50 mu m, (ii) taking 0.1-1 g bismuth oxyhalide catalyst, uniformly dispersing in anhydrous ethanol under ultrasonic vibration, pouring into the step (i) obtained anode film surface, drying at 20-50 degrees C, obtaining bismuth oxyhalide film with thickness of 0.05 mu m, and (iii) taking 2-10 g chitosan or polyimide and 3-10 g polyvinylpyrrolidone, mixing and dispersing in a beaker, adding 0.25-2% acetic acid aqueous solution, heating and stirring to dissolve, adding aldehyde crosslinking agent for 5-20 minutes, and then pouring in the step (ii) obtained bismuth oxyhalide film, obtaining cathode film with thickness of 50 mu m, drying at room temperature, obtaining anode film/bismuth oxyhalide film/cathode film with thickness of 100.05 mu m, which is photo-electro-catalytic film.