Abstract: Acrylic acid was grafted onto PET fiber by the induce of Ar plasma.The process was optimized by evaluating the wettability of samples yielded under different conditions.The dyeing behaviour,calorific properties and infrared spectrogram of treated PET fiber were tested and analyzed.The surface morphological structure of treated PET samples was examined with SEM.The results show that the wettability of the grafted PET fiber was improved remarkably and the grafted fiber had a good durability.The glass transition point of the grafted fiber was not observed by DSC analysis.