Abstract: In this paper, we studied the degradation mechanism of the waste polyester (PET) degradated in glycerol. We used Infrared Spectroscopy (FT-IR) ,Ultraviolet(UV), Mass (MS) , High Performance Liquid Chromatography (HPLC) and (TGA) to analyze the characterization of the degradated product. Firstly, the structures of the degradated product wase got by FT-IR and UV; then we got the molecular structure and molecular weight through Mass; what’s more, we analyzed the degradation product quantitatively with HPLC, at the same time, we combined the TGA analysis to determine the pure of the alcoholysis product, finally, we got the epoxy value through the method of hydrochloric acid-acetone. Synthesize the five analysis, we got the degradation mechanism, and the epoxy value was 0.259.