NOVELTY - A lithium ion battery plasticizer preparing method involves preparing methoxy-poly(ethylene glycol) methacrylate (MPEGM) and hexadecal-poly(ethylene glycol) methacrylate (HPEGM), MPEGM-co-HPEGM copolymer, and MPEG-aluminum acetate by adding polyethylene glycol monomethyl ether (MPEG350, MPEG550, MPEG750) and aluminum isopropoxide to three-necked flask to obtain reactant. The reactant is extracted under vacuum and heated, followed by filling EO unit with MPEG-aluminum ester and inert gas to obtain reacted product, and preparing P(MPEGM-co-HPEGM)/MPEG-aluminum electrolyte film.    USE - Method for preparing lithium ion battery plasticizer.    ADVANTAGE - The method enables preparing lithium ion battery plasticizer with increased ion conductivity, and increased degree of dissociation of lithium salt.    DETAILED DESCRIPTION - A lithium ion battery plasticizer preparing method involves preparing methoxy-poly(ethylene glycol) methacrylate (MPEGM) and hexadecal-poly(ethylene glycol) methacrylate (HPEGM) in 500 ml three-neck flask, adding 200-300 ml anhydrous tetrahydrofuran, 0.1-0.3 mol methoxy-poly(ethylene glycol)(MPEG), hexadecal-poly(ethylene glycol) (HPEG), and 0.12-0.36 mol triethylamine to obtain mixture. The mixture is cooled in an ice water bath to 5 degrees C and stirred till homogeneous solution, followed by dropping 0.12-0.36 mol methacryloyl chloride and 50-100 ml anhydrous tetrahydrofuran slowly and stirring for 2-8 hours to obtain reaction solution. The reaction solution is filtered to remove insoluble substance. The solution is added with dichloromethane and washed with dilute solution of lithium hydroxide, followed by collecting lower layer organic liquid. The solid impurity is washed with saturated sodium chloride water solution to remove solid impurities by rotary evaporation. The resultant solution is dried and filtered to remove residual solid impurity to obtain light yellow oily product, followed by preparing MPEGM-co-HPEGM copolymer by mixing 30-50 wt.% MPEGM 350 and 40-60 wt.% HPEGM to obtain 40-50 g MPEGM/HPEGM monomer mixture. The 10-30 wt.% monomer mixture is added with 0.4-0.8 g initiator azobiisiso-butyrynitrile and 200-300 ml anhydrous tetrahydrofuran in three-necked flask under the protection of inert gas and heated at 60-70 degrees C for 20-30 minutes. The rest monomer mixture is slowly added dropwise and continuously reacted for 3-6 hours to obtain reaction liquid. The reaction liquid is poured in a deionized water, followed by precipitating polymer, filtering at 80-90 degrees C and washing deionized water for several times and drying to obtain dried product. The dried product is placed in an oven to obtain polymer material. The polymer material is mixed with EO unit and lithium salt at a ratio of 4:1-6:1, followed by adding 5-10 ml dimethyl formamide (DMF) as solvent and stirring to obtain uniform transparent thick solution, which is poured in PTFE mold to film forming casting, and placed in oven at 50-60 degrees C to evaporate solvent for 10-15 hours, and dried in vacuum to remove residue dimethyl formamide to take out film. The film is cut into a circular thin film with diameter of 2-3 cm2, followed by preparing MPEG-aluminum acetate by adding polyethylene glycol monomethyl ether (MPEG350, MPEG550, MPEG750) and aluminum isopropoxide at a ratio of 2-3:1 to three-necked flask under an inert gas to obtain reactant. The reactant is extracted under vacuum and heated to 100 degrees C. The EO unit is filled with MPEG-aluminum ester and inert gas to obtain reacted product. The reacted product is placed in a dry box, followed by abbreviating EO units of different MPEG-aluminum acetate such as (MPEG350)3-aluminum as MPEG7-aluminum, (MPEG550)3-aluminum as MPEG12-aluminum and (MPEG750)3-aluminum abbreviated as MPEG16-aluminum, preparing P(MPEGM-co-HPEGM)/MPEG-aluminum electrolyte film by adding 40-60 wt.% P(MPEGM-co-HPEGM), 10-30 wt.% EO units of different MPEG-aluminum acetate, 10-15 wt.% lithium perchlorate, and 5-10 wt.% anhydrous tetrahydrofuran in a tapered bottle and stirring till the lithium salt to be dissolved completely to obtain mixed solution, which is evacuated at room temperature to remove tetrahydrofuran to obtain a viscous yellow liquid. The obtained liquid is poured into PTFE mold and placed in a vacuum oven under inert gas protection at 40-60 degrees C and dried to form film. The film is cut into circular electrolyte film with diameter of 2-3 cm2. The obtained film is placed in a drying box to obtain P(MPEGM-co-HPEGM)/MPEG7-aluminum, P(MPEGM-co-HPEGM)/MPEG12-aluminum or P(MPEGM-co-HPEGM)/MPEG16-aluminum.