Abstract: This paper introduced the theoretical and experimental aspects of grafting soybean protein onto the surface of PAN fiber.The results indicated that through surface hydrolysis,acidchloride reaction and grafting,the protein grafting modified polyacrylonitrile(PAN) fiber was obtained.The elongation breaking strength of the grafted fiber was 1.9～(2.1 cN/dtex,) and the breaking extension was 25%～30%.SEM photographs showed that the surface of PAN fiber was wholly covered by a protein layer after grafting.This demonstrated that the modified PAN fiber with its surface covered by protein could be obtained by grafting protein onto the surface of PAN fiber.