The invention discloses a method for degrading polyethylene terephathalate. The method mainly includes the following steps: 1, strain culture: comamonas testoseroni strain is cultured for 12-18h in a solid medium with inclined surface at 30-37 DEG C; 2, substrate solution preparation: 5-9 parts of substrate solution with the concentration of 1-5g/L are prepared, each part is 50ml and is respectively placed into a 150ml conical flask, and packing up and sterilizing for 25min are carried out at 121 DEG C; 3, substrate degradation: the strain in the step 1 is inoculated into the substrate solution in the step 2, so as to obtain degradation liquor, and shake culture is carried out at the rotating speed of 200r/min and at the temperature of 30-37 DEG C, so as to catalyze degradation on the substrate; 4, substrate degradation ratio detection: 400-190nm wavelength scanning is adopted, and variation of substrate content is judged according to absorption peak at 240nm; 5, substrate degradation product detection: 400-190nm wavelength scanning is adopted, and variation of degradation intermediate product content is judged.