A typical setback of ANAMMOX granules was their flotation when the reactor was run at high loading rates. The effects of Acylated Homoserine Lactones (AHLs) on the characteristics of ANAMMOX granules in high-loaded UASB reactors were investigated. The results showed that the exogenous addition of 30mg/LN-octanoyl-PL-homoserine lactone (C8-HSL) had long-term effects on the settleability of ANAMMOX granules and was able to control the sludge floating effectively. At the beginning of the experiment (0~20d), C8-HSL was added to the reactor R2. While compared with the control group R1, the content of B-EPS in the granular sludge in R2was decreased by 15% and the granular sludge's value of PN/PS dropped from 4.22 to 2.14 on the 100^th day. In addition, the hydrophobicity of the granular sludge in R2 was increased by 26% on the 100^th day. Therefore, the settleability of sludge granules in R2 was improved significantly (the density of the granules was increased by 24%, and the settling velocity of the granules was increased by 90%). During the 100days, no obvious granule floatation was observed in R2. On the 100^th day, the NLR was 12.9kg-TN/(m³·d) and the NRR was up to 11.3kg-TN/(m³·d) in R2. At the same time, the nitrogen removal efficiency was up to 88% in R2. C6-HSL improved the activity of the granular sludge, while C12-HSL had no effects on the characteristics of the granules in the high-loaded reactors.