NOVELTY - Composite film comprises imidazole microcapsule loaded with phosphotungstic acid and sulfonated polyether ether ketone having a sulfonation degree of 55-72% with a mass ratio of 0.025-0.5:1, where the thickness of the composite film is 62-73 microns and the size of imidazole microcapsule is 150-600 nm having a thickness of 4-120 nm, where the amount of phosphotungstic acid loaded in imidazole microcapsule is 50-70%.    USE - The composite film is useful as direct methanol fuel cell proton exchange membrane (claimed).    ADVANTAGE - The composite film is prepared by a simple technique under moderate and controlled conditions.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparing composite film comprising mixing polyether ether ketone with 98% sulfuric acid to obtain 14-18% polyether ether ketone, expanding the mixture for sulfonation reaction in 40-50 degrees C water bath for 13 hour, stirring to produce a brown viscous mixture deposition in deionized water, soaking, rinsing until the pH of the mixture becomes 7, and drying the mixture at room temperature for 48 hour to obtain 55-72% sulfonated polyether ether ketone, adding orthosilicate into 10% volume of alcohol to obtain 5-10% of silicon acid bi-ester solution, mixing silicon acid bi-ester and 25% aqueous ammonia in a volume ratio of 1:0.5-1 to obtain mixed solution, adding the mixed solution into methacryloxypropyl trimethoxy silane, stirring and reacting for 24 hour to obtain silica microsphere surface grafted with reactive double bond, where the mass volume concentration of nitrile in silicon oxide micro-sphere surface is 0.0025-0.00625 g/ml, carrying out ultrasonic dispersing to obtain the suspension of dinitrile, adding bi-vinyl imidazole and methacrylic acid in a volume ratio of 1:1, adding bi-vinyl imidazole with the volume fraction of 0.375-0.75%, and adding water into the suspension, refluxing at 90-100 degrees C for 1.5 hour to obtain the imidazole containing a layer of hybrid micro-sphere, dispersing hybrid surface of the microspheres containing imidazole shell with 10% of hydrofluoric acid solution to prepare 0.008-0.016 g/ml of suspension liquid, standing for 2 hour to obtain the microcapsule imidazole, taking phosphotungstic acid and microcapsule imidazole with volume ratio of 0.1-0.25:1, dispersing imidazole microcapsule in 0.05-0.3 M phosphor-tungstic acid water solution, centrifugally separating, washing, taking imidazole microcapsule loaded phosphotungstic acid and sulfonated polyether-ether-ketone with a mass ratio of 0.025-0.5:1 and taking N,N-methyl amide with mass concentration of 5-12%, ultrasonic dispersing in the N,N-methyl amide for 12-48 hour, adding sulfonated polyether ether ketone, standing for 1 hour, degassing to obtain casting solution, placing the casting solution in 10 cmx 10 cm clean glass plate, drying at a temperature of 60-80 degrees C for 12-24 hours to obtain dry film, performing film preparation process in 2M hydrochloric acid for 24-48 hour, washing with deionized water to neutral, and drying under vacuum to obtain 62-73 mu m thickness of composite membrane.