To modify the physical and chemical properties of polyacrylonitrile, acrylonitrile monomer was copolymerized with the various mole percentage of modifiers, sodium allylsulfonate and sodium methallylsulfonate. The moisture regain of modified copolymer containing strongly hydrophilic group was increased in proportion to the mole percentage of modifier in the copolymer. The anti-static property of modified copolymer was favorably improved in comparison with that of acrylonitrile homopolymer. The inherent viscosity and tensile strength of modified copolymer were decreased slightly. The cationic dyeability (Crystal Violet) of the modified copolymer which was provided with acidic site by modifier was increased.