The accumulation and elimination rules of avermectin in perch (Lateolabraxjaponicus) were studied and the avermectin residues in perch were determined with HPLC-fluorescence method. The perch with initial body weight of (120±15) g were dealt with 0.5 μg/L medicated bath for 20 d. After medicated bath was terminated, the avermectin retained in muscle, liver, gill and blood was determined. The results showed that avermectin could accumulate in muscle, liver, gill and blood of perch, but the enrichment capacity of each tissue was different. The enrichment capacity of avermectin was comparatively strong in the liver, but relatively weak in muscle. The Cmax of liver could reach 87.36 μg/kg，and AUCliver was 12 977.73 (μg/L)·h, whereas the Cmax of muscle was 7.74 μg/kg and AUCmuscle was only 2 105.75 (μg/L)·h. Elimination half-time of avermectin in the muscle, gill, liver and blood of perch were 6.9, 9.5, 8.2 and 10.7 d, respectively. Since many factors affected residues of aquatic animals, pharmacokinetic parameters of the same drug in different aquatic animals were very different. In this condition, when the temperature were 15-18℃, the residues of avermectin in muscle dropped to detection limit after 40 d. This study discussed the pharmacokinetics of avermectin in perch, and analyzed the content variations of the muscle, liver, gill and blood in perch with different time. The dynamic change rules of avermectin were clarified, which would provide theoretical basis for clinical medication in future.