Abstract: A Pyrazosulfuronethyl degradating strain DF12 was isolated from sewage reservoir of the herbicides factory in Hunan, which it belonged to Pseudomonas putida based on the results of physiological,biochemical identification and molecular identification. Single factor experiment showed that the rate of degradation reached to 74.78 % when DF12 optimal culture conditions of degradating pyrazosulfuronethyl in 100 mL flask were shaking volume of 70 mL, inoculum size of 2.0%(OD600=0.80), pH of 7.0.