Abstract: Two efficient strains of synthetic pyrethroid insecticides-degrading bacteria,M6R9 and M5R14,isolated from the tame sludge of sewer in pesticide factory of Hangzhou,which can degrade bifenthrin,fenpropathrin and cypermethrin simultaneously,were identified as Enterobacter aerogenes and Pseudomonas diminuta,respectively.By comparing degradation rates of the two strains independently and in mixed types, it's found that the degradation rate of bifenthrin,fenpropathrin and cypermethrin was related to inoculated amount at OD415nm,and the degradation process was fitted to first-order kinetic equation.Under the optimum inoculated amount at OD415nm=0.2 (the mixed strains M6R9 and M5R14 respectively inoculated OD415nm=0.1 at equal proportion,while the single strain M6R9 or M5R14 inoculated OD415nm=0.2),the degradation rate of mixed strains for bifenthrin,fenpropathrin and cypermethrin (100 mg/L) increased by 2.5% ,3.4% ,2.3% or 14.5% ,14.6% ,15.5% ,and the half-life (T1/2) was shorten by 8.1,14.8,13.1 h or 40.3,50.7,46.4 h,compared with the single strain M6R9 or M5R14 after culturing 3 days in the condition of pH 7.0,30 ℃,180 r/min.It's proposed that there's a synergistic effect between M6R9 and M5R14 on bifenthrin,fenpropathrin and cypermethrin.