NOVELTY - Synthesis of block-type sulfonated polyimide-polybenzimidazole proton exchange film involves adding sodium salt of sulfonated polyimide and organic solvent into dry three-neck flask, stirring, adding polybenzimidazole and catalyst, stirring, heating resultant mixture at 75-85 degrees C for 3.5-4.5 hours, further heating at 175-185 degrees C for 18-22 hours, casting resultant polymer solution into 10 cmx 10 cm film, washing obtained film using 200 mL methanol solution at 75-85 degrees C for 22-26 hours, further washing using 200 mL/L hydrochloric acid solution for 24 hours, and drying.    USE - Synthesis of block-type sulfonated polyimide-polybenzimidazole proton exchange film used for polymer electrolyte membrane fuel cell.    ADVANTAGE - The method enables synthesis of block-type sulfonated polyimide-polybenzimidazole proton exchange film with improved hydrolytic stability, conductivity at high temperature and low humidity conditions, dimensional stability and mechanical property.    DETAILED DESCRIPTION - Synthesis of block-type sulfonated polyimide-polybenzimidazole proton exchange film involves adding 1 equivalent tetramine and polyphosphoric acid into three-neck flask provided with gas inlet, drying tube, gas outlet and mechanical stirrer, stirring, heating at 145-155 degrees C for 25-35 minutes under inert gas atmosphere such that tetramine is uniformly dispersed in polyphosphoric acid, adding 0.8-1 equivalent acid and 0-0.2 equivalent blocking agent, heating resultant mixture at 190-210 degrees C, adding phosphorus pentoxide to enhance absorption of water in reaction product, adding triphenyl phosphine, maintaining temperature at 190-210 degrees C for 18-22 hours, cooling reaction solution to room temperature, washing cooled product using deionized water to remove polyphosphoric acid, and drying obtained polybenzimidazole at 40 degrees C in a vacuum oven, adding 1 equivalent sulfonated diamine, phenol solvent and protonated protection reagent into dry three-neck flask, stirring under inert gas atmosphere until sulfonated diamine is completely dissolved, adding 1-2 equivalent dianhydride, 0-1 equivalent non-sulfonated diamine and 2-4 equivalent catalyst, stirring at room temperature for 30 minutes, heating resultant mixture at 75-85 degrees C for 3.5-4.5 hours, further heating at 175-185 degrees C for 18-22 hours, cooling reaction mixture to 75-85 degrees C, adding organic solvent to dilute high-viscosity solution, adding resultant solution into acetone, generating filamentous precipitate, washing the precipitate using acetone to remove solvent, adding washed precipitate into saturated sodium chloride solution, stirring continuously for 48 hours, filtering, washing the filtrate using deionized water for 3 times, vacuum-drying at 100 degrees C for 22-24 hours, obtaining sodium salt of sulfonated polyimide, changing molar ratio of sulfonated monomer and non-sulfonated monomer to obtain different sulfonated anhydride-terminated sulfonated polyimide, adding sodium salt of sulfonated polyimide and organic solvent into dry three-neck flask, stirring under inert gas atmosphere until sodium salt of sulfonated polyimide is completely dissolved, adding polybenzimidazole and catalyst, stirring at room temperature for 25-35 minutes, heating resultant mixture at 75-85 degrees C for 3.5-4.5 hours, further heating at 175-185 degrees C for 18-22 hours, casting resultant polymer solution into 10 cmx 10 cm film at 100 degrees C, washing obtained film using 200 mL methanol solution at 75-85 degrees C for 22-26 hours, further washing using 200 mL/L hydrochloric acid solution for 24 hours, and drying.