An anaerobic sequencing batch biofilm reactor was used to explore the combined effect mechanism of anammox under the co-existence conditions of quinoline (50~200mg/L) and microplastics (PET-MPs) (20~100mg/L). With the increase of the concentrations of quinoline and PET-MPs, the performance of Anammox first decreases and then gradually recovers, and recovery time of reversible inhibition was positively correlated with the concentration of combined pollutants. The specific anammox activity (SAA) decreased from 22.8mg N/(g VSS·h) in stage C1 to 16.2mg N/(g VSS·h) in stage C3, while the corresponding reactive oxygen species (ROS) production increased by 55.7%, indicating that the inhibition of Anammox was enhanced under combined pollution. Extracellular polymer (EPS) analysis revealed that an increase in the concentrations of quinoline and PET-MPs would lead to a rapid decrease in the EPS content of the biofilm from 75.3mg/g VSS to 39.2mg/g VSS. The significant reduction in protein (PN) secretion, which in turn led to a significant decrease in PN/PS, indicates a decline in the structural stability of the Anammox biofilm. High-throughput sequencing revealed that the concentration of quinoline /PET-MPs increased, while the microbial community diversity and richness indices decreased. The relative abundance of Candidatus_Brocadia decreased from 1.73% to 1.24%, while the relative abundance of Denitratisoma changed little. However, the relative abundance of anaerobic heterocyclic degrading bacteria increased significantly.