In this paper, N-isopropylacrylamide (NIPAAm), as hydrophilic group, is successfully grafted onto nylon sieve by γ-rays radiation induced graft polymerization. The degree of grafting (DG) is acquired by weighing method. The effect of monomer concentration on DG is studied under the condition of methanol as the solvent and copper sulphate as the inhibitor. Both of samples before and after the graft polymerization are tested using FT-IR, TGA for thermal decomposition temperature, SEM for the surface topography and contact angle (CA) against water for the hydrophilicity. The results show that the thermal decomposition temperature of grafted sample is lower than that of the original sample; the apparent size of the yarn of the grafted sample is bigger than that of the original sample. Furthermore, the value of CA of grafted sample decreases gradually with the increasing value of DG, which indicates the hydrophilicity of the samples is improved.Cited