TECHNOLOGY FOCUS - POLYMERS - Preparation: The preparation method of lithium ion polymer electrolyte film comprises (1) preparation of high amorphous phase polymer substrate: dissolving large monomer of PEO with 200-1000 of average molecular weight, small monomer of alkenes and azodiisobutyronitrile according to 1:1-100: 0.01-0.11 of mol ratio into methanol solvent in a reaction kettle, where weight ratio of large monomer of PEO and the methanol solvent is 1:11-15; making reactants react at 70-90 degrees C under conditions of magnetic stirring and nitrogen atmosphere for 8-12 hours and obtaining methanol solution of copolymerization product; (2) compounding of electrolyte materials: adding LiBF4 and Li- beta -Al2O3 nano-powder to methanol solution of copolymerization product to mixing into even slurry, where dosage of LiBF4 is 0-20wt.% of the obtained lithium ion polymer electrolyte film, while the Li- beta -Al2O3 nano-powder is 5-30wt.%; and (3) forming film with flow casting method: after de-aerating slurry by standing, carrying flow casting at 40-60 degrees C in nitrogen atmosphere; and forming the film after the solvent is volatilized, where rotating speed of flow casting is controlled at 0.18-0.60 m/minute. Preferred Components: The small monomer of alkenes is acrylonitrile, lithium acrylate, butyl acrylate, methyl methacrylate or acrylamide. Preferred Process: In (2), it comprises filtering methanol solution containing copolymerization product, and purifying and drying it in vacuum to obtain the copolymerization product; thermally dissolving the copolymerization product to tetrahydrofuran; adding LiBF4 and Li- beta -Al2O3 nano-powder to the solution for mixing into even slurry, where dosage of LiBF4 is 0-20wt.% of the obtained lithium ion polymer electrolyte film, while the Li- beta -Al2O3 nano-powder is 5-30wt.%. The Li- beta -Al2O3 nano-powder is prepared by sol-gel method comprising taking aluminum nitrate and lithium nitrate according to that (Li+)/(Al3+) is 1:50 for preparing into 1 mol/L of solution and mixing uniformly; as stirring violently, adding dropwise 1 mol/L of ammonium hydrogen carbonate solution to adjust pH of the mixed solution to 4.10-4.20; standing it for aging for 40-50 hours after 0.5-2 hours of violent stirring; grinding it after drying in a dry box at 40-70 degrees C, obtaining dry gel powder; carrying out heat treatment to it at 800-1100 degrees C and preserving heat for 2-3 hours; cooling, grinding, and obtaining Li- beta -Al2O3 fast ion conductor nano-powder. The preparation of large monomer of PEO comprises getting polyethyleneglycol with 200-1000 of average molecular weight, triethylamine and acryloyl chloride ready according to 1:1.8-3.0:2.8-4.0 of mol ratio, and getting toluene solvent ready according to that weight ratio of polyethyleneglycol and toluene is 1:3-12; adding the polyethyleneglycol and triethylamine to the reaction kettle in turn at 35-45 degrees C as magnetic stirring, and slowly adding acryloyl chloride; after finishing adding, continuing to preserve heat and stir for 4-8 hours; after finishing the reaction, filtering to remove generated amine salt; evaporating the filtrate to remove partial solvent; next adding ether precipitator of which volume is greater than or equal to 4-12 times volume of rest filtrate; drying the precipitated product in vacuum after filtering and obtaining large monomer of polyoxyethylene having double bond on its two ends. The preparation of large monomer of PEO comprises getting polyethylene glycol monoethyl ether with 200-1000 of average molecular weight, triethylamine and acryloyl chloride ready according to 1:1.0-1.8:1.6-2.2 of mol ratio, and getting toluene solvent ready according to that weight ratio of polyethylene glycol monoethyl ether and toluene is 1:3-12; adding the polyethylene glycol monoethyl ether and triethylamine to the reaction kettle in turn at 35-45 degrees C as magnetic stirring, and slowing adding acryloyl chloride; after finishing adding, continuing to preserve heat and stir for 4-6 hours; after finishing the reaction, filtering to remove generated amine salt; evaporating the filtrate to remove partial solvent; adding ether precipitator of which volume is greater than or equal to 4-12 times volume of rest filtrate; drying the precipitated product in vacuum after filtering, and obtaining large monomer of polyoxyethylene having double bond on its one end. The lithium ion polymer battery is formed into square shape or coiled into cylindrical shape.