Abstract: Quorum sensing signal molecules have a significant influence on the microbial behavior and the contents of functional microorganisms in the wastewater treatment process, but its impact on the nitrous oxide (N₂O) generation in the biological nitrogen removal process is still unclear. To explore the mechanism between quorum sensing and N₂O generation, two kinds of N-acylated homoserine lactones (AHLs) signal molecules N-hexanoyl-L-homoserine lactone (C₆-HSL) and N-octanoyl-L-homoserine lactone (C₈-HSL) were used to study the effects of exogenous addition of AHLs on treatment performance, N₂O production characteristics and microbial community structure in an AO process. The results showed that: (1) The signal molecules of C₆-HSL and C₈-HSL could significantly enhance the biological nitrogen removal. The nitrification rates of the two bioreactors increased observably. The NH₄⁺-N removal rate increased by 1.7% and 2.2%, and the TN removal rate increased by 7.6% and 5.4%, respectively. However, the COD_Cr removal rates did not change obviously. (2) With the addition of C₆-HSL and C₈-HSL, the total N₂O production in the systems increased by 39.0% and 11.0%, respectively. Nitrifier denitrification was the main N₂O producing approach in the aerobic treatment stage. (3) Microbiological analysis showed that the microbial community structure and the functional microorganisms involved in biological nitrogen removal in activated sludge varied obviously. With the addition of C₆-HSL and C₈-HSL, the relative abundance of AOB (ammonia oxidizing bacteria) increased from 0.3% to 0.5% and 0.4%; the relative abundance of NOB (nitrifying bacteria) increased from 0.03% to 0.07% and 0.08%; the relative abundance of DNB (denitrifying bacteria) increased from 6.3% to 8.5% and 7.5%, respectively. The study indicated that AHLs exogenous signaling molecules could increase the relative abundance of functional bacteria AOB, NOB and DNB in biological nitrogen removal processes, resulting in an enhancement of the treatment performance and N₂O generation.