Glycolysis of poly(ethylene terephthalate) with ethylene glycol was carried out with the catalysts of sulfated cobalt oxide (SO42-/Co3O4) and zinc-modified sulfated cobalt oxide (SO42-/Co-Zn-O). The catalysts prepared at different calcination temperatures have been characterized by various techniques. These techniques include X-ray diffraction, Raman spectrum, gas adsorption analysis, NH3-temperature programmed desorption, and IR spectroscopy of pyridine adsorption. The performances of these catalysts on the depolymerization of PET under mild conditions were studied, and relationships between the catalysts' textural properties, the surface acidity, and the catalytic activity have been investigated. The experimental results showed that the catalytic activity on glycolysis of PET was significantly improved by the catalysts of binary sulfur oxides of SO42-/Co-Zn-O. The conversion of PET obtained on SO42-/Co-Zn-O-300 degrees C was 96%, and the selectivity of BHET was 75%, after 3 h at 180 degrees C under atmospheric pressure.