Poly(ethylene terephthalate)(PET) was glycolyzed by ethylene glycol(EG) at the various mole ratio of ethylene terephthalate(ET) group to EG, reaction time, temperature, and pressure in the presence of sodium acetate as a catalyst(0.5 wt.% of PET). The glycolyzed products were analyzed by hydroxyl value measurement and high performance liquid chromatography(HPLC). Under atmospheric pressure, PET was depolymerized to an equilibrium after the reaction time of 10 hrs. On the other hand, equilibrium was attained within 2 hrs under elevated pressure. The components of glycolyzed product were BHET and higher oligomers, mostly dimer and primer. It was found that the rate of depolymerization is dependent on reaction condition, such as mole ratio of ET : EG, reaction time, temperature and pressure. Glycolytic depolymerization rate of PET is proportional to the concentrations of ester group of PET and hydroxyl group of EG. The activation energies of glycolytic depolymerization under ambient, 12, 25, and 50 arm were 22.03, 19.41, 18.03, and 15.34 kcal/mol for the mole ratio of 1:3(ET : EG), respectively.