TECHNOLOGY FOCUS - POLYMERS - Preferred Compound: The cyclic functional group in repeating unit of copolymer has cycloalkene aryl structure or cycloalkadiene aryl structure, preferably cyclobutene aryl structure or cyclobutadiene aryl structure. The repeating unit having cyclic functional group, is represented by formula (I), preferably formula (II). The ion electroconductivity region of repeating unit of copolymer has a structure which can be interacted with electrolyte salt through oxygen atom. The ion electroconductivity region is represented by formula (III). The repeating unit having ion electroconductivity region, is of formula (IV). The copolymer is a block copolymer that has block chain (A) having repeating unit (I) and block chain (B) having repeating unit (IV), which are arranged as blocks B-A-B. The copolymer has number average molecular weight of 5000-1000000.R1-R4,R8-R13,Z1,f,X,Y,Z,a,b,d=same as defined above, were Z1 is preferably ester bond;R5=halogen or organic group;ande=0-3.Preferred Electrolyte: The solid polymer electrolyte is formed by ring-breakage reaction of the composition containing copolymer and electrolyte salt. EXAMPLE - A polymer of Blenmer PME-1000 (methoxy polyethylene glycol monomethacrylate) having molecular weight distribution of 1.92 and weight average molecular weight of 285000, was prepared. The obtained polymer (in g) (5), chloropentamethyl cyclopentadienyl bis(triphenylphosphine)ruthenium (0.02), styrene (0.4), 4-vinyl benzo cyclobutene (0.4) and toluene (24) were added to a flask, and mixed uniformly. Then, di-n-butyl amine (0.01) was added to the mixture, and polymerized at 100degreesC. After polymerization, the reaction solution was cooled and the metal complex was removed by column chromatography. The solvent was evaporated under reduced pressure, to obtain viscous residue. The obtained residue was dried under reduced pressure at 60degreesC for 5 hours, to obtain block copolymer. The obtained block copolymer had weight average molecular weight of 300000, and contained methoxy polyethylene glycol monomethacrylate, styrene and 4-vinyl benzo cyclobutene in weight ratio of 95:3:2. The block copolymer was dissolved in acetone. Then, lithium compound (Li(CF3SO2)2N) was added to the obtained solution. Subsequently, acetone was volatilized, to obtain solid polymer electrolyte film of 100 microns thickness. The obtained electrolyte film had high strength and ionic electroconductivity.