Abstract:Three standard test methods for evaluating the toxicity of chemicals to aquatic organisms were applied to assess the toxic effects of 1-octyl-3-methylimidazolium PF6([C8mim]PF6)on the three aquatic organisms: Chlorella vulgaris, Daphnia magna and zebra fish. Growth and chlorophyll a content of C. vulgaris were inhibited in the experimental content of [C8mim]PF6, the inhibiting effect increased significantly with increasing concentrations, and the toxic effects on chlorophyll a content were stronger than that of growth. The C. vulgaris cell even would be lethal in the higher concentration group (200mg/L). The toxic effects of [C8mim] PF6 was high-toxic to Daphnia magna, while was low-toxic to zebra fish, and the 48h LC50 and 96h LC50 was 4.47mg/L and 126.08mg/L, respectively. EC50/LC50 changed regularly with the test time. Maybe the two main reasons leading to the potential threat to the aquatic organisms were the affinity of [C8mim]PF6 with algae and lipophilic property itself.