Abstract: The acute toxicity and safety concentration of non-ionic ammonia and ammonia-N to juvenile Amur sturgeonAcipenserschrenckiwith body weight of (1.7 ±0.2) g (A1),(3.6 ±0.6) g (A2), and (10.3 ±1.5) g(A3) were studied at water temperature of (22±1)℃, pH 7.6, and dissolved oxygen (DO) level of 7.0-8.0 mg/L. The results showed that there was a significant positive correlation between the median lethal concentration(LC50) and safety concentration of non-ionic ammonia and ammonia-N levels and body weight of the Amur sturgeon juveniles. Under the experimental conditions, the 96 h LC50of ammonia-N were found to be 5.30 mg/L in A1,10.20 mg/L in A2,and 12.30 mg/L in A3,with safety concentration of 0.53 mg/L in A1,1.02 mg/L in A2,and 1.23 mg/L in A3. The 96 h LC50of non-ionic ammonia-N were found to be 0.13 mg/L in A1,0.26 mg/L in A2, and 0.28 mg/L in A3, with safety concentration of 0.01 mg/L in A1,0.03 mg/L in A2, and 0.03 mg/L in A3.