【Background】Several reports about the toxicity and the effect of pesticides on aquatic organisms have been published, but few papers have dealt with Fluroxypyr effects on aquatic organisms. This paper examined the acute toxicity and the safety of Fluroxypyr on fish. 【Method】Acute toxicity and safe concentrations of Fluroxypyr for Ctenopharyngodon idellus, Hypophthalmictuthys molitrix and Carassius auratus were investigated using standardized laboratory procedures. Tests were conducted at water temperature of 25 ℃ ±1 ℃. 【Result】The results indicated that median lethal concentrations （LC50） declined with increased duration of exposure to chemicals. The 96 h LC50 of Fluroxypyr for C.idellus, H.molitrix and C.auratuswere 0.4764 mg·L-1, 0.3962 mg·L-1 and 0.6918 mg·L-1, and the safe exposure concentrations were 0.0476 mg·L-1, 0.0396 mg·L-1 and 0.0692 mg·L-1 respectively. 【Conclusion and significance】This research confirmed the acute toxicity of Fluroxypyr on C.idellus, H.molitrix and C.auratus, and its belonging to high toxicity substances. The paper provided a scientific basis for risk assessment of Fluroxypyr and environmental safety management.