Abstract: In order to investigate the inhibitory effect of the toxic organic matter of phenol on anammox granular sludge, the removal rate of ammonia nitrogen ( \rmNH_4^ + -N) and nitrite nitrogen (NO₂ ⁻-N) in anammox granular sludge under different phenol conditions (50 and 100 mg/L) was studied. The reasons for the degradation of granular sludge performance were analyzed by integrating the secretion of extracellular polymeric substances (EPS) and the change trend of microbial community. The results showed that phenol inhibited the denitrification performance of anammox granular sludge. When the phenol concentration was 50 and 150 mg/L, the removal rate of \rmNH_4^ + -N was reduced by 15.05% and 24.35%, respectively. Phenol stimulated the secretion of microbial EPS in granular sludge to resist its toxic stress. When the phenol concentration was 50 and 150 mg/L, the total EPS content of granular sludge increased by 43.62% and 57.29%, respectively. The microbial community of the anammox granular sludge changed under different phenol conditions. Under the phenol concentration of 50 and 150 mg/L, the relative abundance of Planctomycetes distributed by anammox bacteria decreased from 41.01% to 38.52% and 33.84%, respectively. Through the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) prediction analysis, it was found that the key metabolic pathways related to anammox bacteria was inhibited, and the metabolism of functional bacteria related to the denitrification of granular sludge was affected by phenol.