Alkaline hydrolysis of catalytic process conditions of waste polyacrylonitrile fiber was studied in the experiments. The structure of hydrolyzate of waste polyacrylonitrile fiber and its graft copolymerization with poly(ethylene glycol) product were investigated by a Fourier transformation infrared spectroscope. The factors of the poly(ethylene glycol) with molecular weight, the consumption of catalyst, graft copolymerization temperature on graft copolymer was studied by differential scanning calorimeter. The crystal structure of pure poly(ethylene glycol) and graft copolymer were investigated using a polarizing optical microscope. The Fourier transformation infrared spectroscope results indicated that the amide bond existed in hydrolyzate of waste polyacrylonitrile and ether linkage existed in graft copolymer therefore, it could be proven that the cyano group turned into polyacrylamide cyano in the process of base catalysis and the success of graft polymerization to achieve the desired product. The polarizing optical microscope results showed that the pure poly(ethylene glycol), graft copolymer had different crystal structures at different temperatures. The differential scanning calorimeter results indicated that graft copolymer had a high latent heat storage capacity of more than 100 J/g. The melting temperature of hydrolyzate of waste polyacrylonitrile fiber and its graft copolymerization with poly(ethylene glycol) increased with the increase of the molecular weight of poly(ethylene glycol) and the amount of the chain extender. Cooling curves of graft copolymer showed that it had good insulation properties.