NOVELTY - A polymer electrolyte comprises 35-45 parts ion liquid, 2-5 parts emulsifier, 25-35 parts lithium polymer derivative, appropriate amount of solvent A and B, 5-8 parts lithium salt and 6-12 parts base material.    USE - Polymer electrolyte for use in a lithium ion battery (claimed).    ADVANTAGE - The electrolyte has high ionic conductivity, and can be prepared in a simple, easy and cost-effective manner.    DETAILED DESCRIPTION - A polymer electrolyte comprises 35-45 parts ion liquid, 2-5 parts emulsifier, 25-35 parts lithium polymer derivative, appropriate amount of solvent A and B, 5-8 parts lithium salt and 6-12 parts base material, where the ion liquid is 1-ethyl-2-methylpyrazole tetrafluoroborate, 1-methyl-3-ethyl imidazole ethylene imine, N-methyl propyl pyrrole trifluoromethane sulfonamide, N,N-diethyl-N-methyl(2-methoxyethyl)ammonium tetrafluoroborate, the emulsifier is alkyl phenol polyoxyethylene ether formaldehyde, aralkyl phenol polyoxyethylene ether formaldehyde and polyoxyethylene polyoxypropylene copolymer, the lithium conducting polymer is polypropylene oxide, polyalkylene succinate, polyvinylidene fluoride and polyvinyl acetate, the solvent A is ethylene oxide, toluene, acetone, acetonitrile and tetrahydrofuran, the solvent B is dimethyl formamide, dimethyl acetamide, N-methyl pyrrolidone and dimethyl sulfoxide and the basal body material is polysulfone, PVC, polyacrylonitrile, polyvinylidene fluoride and polyether ketone. An INDEPENDENT CLAIM is also included for a method for preparing polymer electrolyte, which involves dissolving 25-35 pts. wt. lithium polymer in solvent A to form solution, adding 2-5 pts. wt. ion liquid and 35-45 pts. wt. into solution, stirring the solution slowly at speed of 40-80 rpm for 20-30 minutes to obtain micro liquid, adding obtained micro liquid into polymerization kettle for self-cross linking reaction to form core of ionic liquid and lithium polymer as shell layer of with tiny granule of micro-capsule structure, drying obtained product, dispersing dried product into solvent B, adding 6-12 pts. wt. lithium salt and 5-8 pts. wt. base material, dissolving the mixture to form casting film liquid, stirring the casting liquid, de-foaming the liquid under vacuum, casting the film in glass plate for 40-60 seconds, soaking the gel bath in curable film-forming and drying to obtain polymer electrolyte film.