Abstract: Ivermectin (IVM) is a widely applied veterinary pharmaceutical which is used in large amount to treat livestock. It has been a potential environmental problem, that the drug often appears intact in the metabolite of livestock, and its transport from soil to surface water via runoff. In natural environment, dissipation is relatively slow, and the residues can cause mortality in a diverse range of invertebrates. So ivermectin may destroy the aquatic ecosystems. To evaluate the potential toxicity of ivermectin to aquatic organisms, we simulated a natural riverway environment when monitoring the degradation speed of it, and then chose seven aquatic organisms which take up different ecological riche to test acute toxicity by national standard metords. The results displayed that the degradation of Ivermectin (IVM) in water environment was slow, and the degradation rate of IVM in sediment was only 28.3% of 70 days’ experiment under 25℃. The results showed no obviously toxicity to Photobacterium phosphoreum and the 96h EC50 to Chlorella vulgaris was 19.80 mg/L, it did not exhibit high toxicity. But the toxicity of IVM to Brachydanio rerio, Gambusia affinis, Carassius auratus, Macrobrachium rosenbergii and Daphnia magna were relatively higher, and date was 40.48 μg/L (96h LC50), 34.81 μg/L (96h LC50), 13.79 μg/L (96h LC50), 7.87 μg/L (96h LC50) and 4.81 ng/L (24h LC50) respectively. IVM would influence the aqua-biology obviously when the drug residue appeared in water environment, so it is necessary to learn more on ivermectin.