Poly(ethylene terephthalate) (PET) was depolymerised glycolytically by using glycols such as ethylene glycol (EG), propylene glycol (PG), and butylene glycol (BG) in the presence of metal acetate catalyst (0.5wt.% of PET). The formation reaction and the equilibrium of glycolyzed products were analyzed by hydroxyl value measurement and high performance liquid chromatography (HPLC). The efficiency of the catalyst was in the order of zinc acetate manganese acetate>sodium acetate. And the rate of depolymerization of the glycols used was decreased in the order of EG>PG>BG. The activation energy of glycolytic depolymerization under 25 atm in the absence of catalyst was 23 kcal/mole for the mole ratio of 1:3 (ET:EG). The correlation between DP of glycolyzed product by hydroxyl value measurement and that obtained from HPLC was quite good.