Solid superacid sulfated titania (SO42-/TiO2) was prepared by impregnation of titanium hydroxide with an aqueous solution of (NH4)2SO4, and then calcined at different temperatures. The structural properties of these samples were investigated using XRD, BET, and DSC. Surface acidity of the catalysts were tested by FT-IR, XPS, and NH3-TPD. The SO42-/TiO2 calcined at 340 °C showed the strongest acid strength. The catalytic activity of the catalysts was evaluated in the depolymerization of polythene terephthalate (PET) with ethylene glycol (EG) by varying different parameters. Experimental results were correlated to the textural properties and surface acidity. The catalyst SO42-/TiO2 calcined at 340 °C exhibited maximum catalytic activity, with the conversion of PET as high as 72.9%, which may be due to the amorphous phase and the strongest acid strength. When the reaction temperature was at 194 °C, the conversion of PET was 100%, and the yield of the bis-2-hydroxyethyl terephthalate (BHET) monomer was 61.7%.