This article from the polyethylene terephthalate (PET) of chemical structure. Combined with the special nature of subcritical water. Hydrothermal method is used to make PET hydrolysis under neutral condition to terephthalic acid (TPA) and ethylene glycol (EG). Through discussion on the effect of filler ratio, reaction time and reaction temperature on the PET hydrolysis rate and the yield of TPA. Research to determine the optimal hydrolysis conditions: feed ratio is 10, experimental temperature is 250℃, reaction time is 7h. Under the optimal conditions, PET PET degradation rate can reach 92.9%, the yield of TPA is 86.4%, the purity of TPA is 98.251% and the acidity of TPA up to 657.14 mgKOH/g. The study found that zinc acetate can accelerate the hydrolysis of PET. And has carried on the preliminary exploration on the hydrolysis mechanism of PET in subcritical water conditions.