The kinetics of nitrification inhibition，the components of polymeric substances on extracellular and oxygen uptake rate(OUR)of partial nitrification sludge were studied at various concentrations of phenol that was served as short-term toxic inhibitor.The results showed that rate of ammonia nitrification reduced by 37% due to inhibition effect of phenol on the ammonia oxidation bacteria.Under low phenol concentrations(<80 mg·L-1)，it followed Monod’s kinetics for single molecule inhibition，indicating that was a kind of reversible inhibition，and OUR achieved at 20—25 mg O2·L-1·h-1 after the rescission of inhibition.The inhibition constant(52.871 mg·L-1)of mixed sludge system used in this study was far larger than that of an enrichment nitrifier culture.In addition，the phenol promoted the starting of microbial self protection mechanism that could produce more extracellular polymeric substances(EPS)to resist environment change.With the phenol concentrations up to 135 mg·L-1，proteins and carbohydrate in EPS increased up to 87.4% and 311.7% respectively.The ratio of proteins to carbohydrates fell from 22.1 to 3.80 with the increasing initial COD/N.