NOVELTY - A ternary polymer, is new.    USE - The polymer is useful for preparing polymer lithium ion battery (claimed).    ADVANTAGE - It has simple techniques, low-cost and abundant raw materials, and is suitable for industrialization preparation of polymer lithium ion.    DETAILED DESCRIPTION - A ternary polymer of constitutional formula (I), where w is 1 to 1.5 ten thousand, is new. INDEPENDENT CLAIMS are:    (1) a preparation method of self-supporting lithium ion battery gel polymer electrolyte comprising: (a) adding emulsifying agent whose mass percent is 1-3% into de-ionized water whose mass percent is 60-70% for dissolving in presence of N2, and adding monomer methyl methacrylate whose mass percent is 25-35%, acrylonitrile and vinyl acetate monomer, stirring uniformly, adding 0.1-4% of initiator whose mass percent is 55-65% by constant voltage filler for reacting; preparing white emulsion after reacting for 5-7 hours, pouring the white emulsion into aluminum sulfate (Al2(SO4)3) solution whose volume is 1-1.5 times of the reaction volume and mass concentration is 2-5%, stirring for breaking emulsion, bathing for 2-5 times by de-ionized water at 50-70 degrees C, and washing for 2-5 times by anhydrous alcohol, to prepare white polymer above, drying the prepared white polymer for 24-36 hours at vacuum drying cabinet at 50-70 degrees C; (b) dissolving the polymer into N-N-dimethylformamide till the mass percent of the polymer is 5-10% at 60-80 degrees C; coating the prepared ropy solution to a clean glass plate after dissolving completely, fixing the thickness of the film; and dipping the film with the glass plate into a de-ionized water groove, to prepare white film; flushing the film for 0.5-1 hour by running water, dipping for 1-2 hours in de-ionized water, and drying the film for 20-30 hours at vacuum drying cabinet, to prepare the self-supporting lithium ion battery gel polymer film; and (c) dipping the self-supporting lithium ion battery gel polymer film into electrolyte for 20-40 minutes in a glove box to prepare self-supporting lithium ion battery gel polymer electrolyte;    (2) a self-supporting lithium ion battery gel polymer electrolyte prepared by the method of (1); and    (3) use of self-supporting lithium ion battery gel polymer electrolyte of (2) for preparing polymer lithium ion battery.