Graft copolymerization of acrylic acid on the surface of poly(ethylene terephthalate)(PTE)ber was investigated using low temperature plasma treatment. Argon plasma was used as an initiator on PET fiber and followed post copolymerization by inducing acrylic acid vapor under required conditions. The topographical change of grafted PET film surface was evaluated by SEM and roughness tester. The grafted feature and the grafting yield of poly(acrylic acid) were evaluated by SEM and FT-NMR respectively. The results obtained are as follows; 1. The surface of PET fiber was etched and activated by plasma treatment. 2. On the roughness of plasma grafted PET film, it can be seen that the longer the plasma treatment time, the lower the height of wave and the spreader the wave width. 3. The grafting of poly(acrylic acid) on PET fiber can be detected by H1-NMR.