Alkaline hydrolysis of PET fibers and the change in structure thereby were investigated with weight loss, density, tensile strength, moisture regain and dyeing behaviors. Benzyl alcohol was used an accelerating agent for alkaline hydrolysis. As a result, it was shown that the weight loss of PET fiber pretreated with 5% benzyl alcohol was increased compared with that of the fiber treated only in sodium hydroxide solution. The rate constant of dissolution of alkaline hydrolysis was dependent on temperature and sodium hydroxide concentration. The loss of tensile strength was decreased with the decrease of weight loss. The hydroysis improved wicking and wetting of PET fibers. As the weight loss of PET fibers increased, the uptake of the dyes increased.