NOVELTY - In an inert atmosphere, an inorganic nanopowder is added to an organic solvent and ultrasonically dispersed. A fluorinated polyanionic polymer is added and dissolved. An active composite component is added to the mixed solution. A crosslinking catalyst is added to the mixed solution and stirred to obtain a film-forming solution. The film-forming solution is applied on a substrate, and maintained at 60-80 degrees C for 10-24 hours and at 100-200 degrees C for 6-24 hours. Impurity ions are removed to obtain a fluorinated polyarylene ether composite anion-exchange film.    USE - In-situ polymerization preparation of fluorinated polyarylene ether composite anion-exchange film for use in all-vanadium redox flow batteries, polymer electrolyte fuel cells, direct methanol fuel cells, ion-exchange resins, membrane separation, and sensors.    ADVANTAGE - The method enables in-situ polymerization for preparation of fluorinated polyarylene ether composite anion-exchange film having excellent dimensional stability, mechanical strength, and ionic conductivity, and low vanadium ion permeability.    DETAILED DESCRIPTION - In an inert atmosphere, an inorganic nanopowder is added to an organic solvent and ultrasonically dispersed at 0-30 degrees C for 0.5-2 hours. A fluorinated polyanionic polymer is added to the mixed solution and stirred for complete dissolution. The mass ratio of nanopowder and polymer is 1-25%. The mass ratio of polymer and solvent is 5-20%. An active composite component is added to the mixed solution such that the mass ratio of active composite component and polymer is 1-40%. A crosslinking catalyst (0.1-10 wt.%) is added to the mixed solution at 0-30 degrees C and uniformly stirred to obtain a film-forming solution. The film-forming solution is applied on a substrate, and maintained at 60-80 degrees C for 10-24 hours and at 100-200 degrees C for 6-24 hours. Impurity ions are removed using deionized water, to obtain a fluorinated polyarylene ether composite anion-exchange film. The fluorinated polyanionic polymer is of formula (I) and has a number average molecular weight of 5000-200000 and a functional degree of 15-95%.    Ar=group of formula (i) or (ii);    R=H or R'f;    R'f=-N+(-CH3)2(-CH2).X-, -N+(-C2H5)3,X-, -P(-CH3)2(-CH2).X-, or group of formula (iii) or (iv);and    X=F-, Cl-, Br-, I- or OH-.