Ultra-performance liquid chromatography tandem mass-spectrometry was used to study the environmentalbehavior of avermectin (AVM) in a simulated aquaculture pond ecosystem. AVM degradation in water, as well as theaccumulation and elimination of AVM in sediments, Elodea nuttallii, and fish and crab tissues were explored. The resultsshowed that 6 μg/L AVM had a half-life of 63.8 h in the simulated pond. At the same time, AVM was transferred tothe sediment, E. nuttallii, and aquatic animals. The peak AVM concentration, concentration time curve, and half-life insediment were 1.25 μg/kg, 469.2 μg/(kg·h), and 115.5 h, respectively. The corresponding values in E. nuttalliiwere 8.75 μg/kg, 2521.7 μg/(kg·h), and 315.0 h, respectively. These results indicate that AVM was absorbed and enrichedin E. nuttallii. In the simulated system, crucian carp (Carassius auratus gibelio) absorbed AVM from water, andpeak blood, kidney, gill, liver, and muscle concentrations were 50.9 μg/kg, 45.37 μg/kg, 21.25 μg/kg, 15.47 μg/kg, and11.9 μg/kg, respectively. AVM was only detected in the gill of Chinese mitten crab (Eriocheir sinensis) at a peak concentrationof 8.08 μg/kg but was not detected in hemolymph, muscle, or hepatopancreas. The bioconcentration factorsin descending order were crucian carp > E. nuttallii > Chinese mitten crab > sediments. These results demonstrate differentabsorption and enrichment in different environmental components and tissues in the same aquatic animal.