Norfloxacin is an efficacious broad-spectrum antibiotic that has been used widely to prevent and controlfish bacterial diseases. However, no comprehensive study has examined the toxicity of norfloxadin to aquaticanimals. Siberian sturgeon is the principle sturgeon species cultured in China and has high scientific research andproduction value. Quinolones occasionally cause an abnormal spinal column in Siberian sturgeon when used tocontrol bacterial diseases. Thus, we investigated the accumulation rule and toxicity of different norfloxadin dosagesand exposure times in Siberian sturgeon. Norfloxacin was given orally to experimental fish at dosages of 0,30 mg/kg, 50 mg/kg, and 100 mg/kg for 3–5 d. Blood, liver, kidney, and cartilage were collected for 24–240 h. Thequantities of drug retained in the four tissues were determined, and histological sections of the liver, kidney, andcartilage were observed. The results showed that the concentrations of norfloxacin in the four Siberian sturgeontissues increased gradually with increasing norfloxadin dosage and time in a trend of kidney > cartilage > liver >serum. Significant differences in liver, kidney, and cartilage drug concentrations were detected when norfloxadinwas given to fish at the same dosage but for different durations. These differences disappeared after withdrawal for240 h. The histology indicated that the liver and kidney were damaged when norfloxadin was given to fish at 50mg/kg for 5 d, and the damage appeared to be more serious at 100 mg/kg for 3–5 d. Damage to the liver, but notthe kidney, recovered gradually during the 240 h withdrawal. The number of chondrocytes near the perichondriumdecreased in cartilage when norfloxadin was given at 100 mg/kg for 3–5 d but recovered gradually during the 240h withdrawal. These results suggest that the norfloxadin dosage should be no more than 50 mg/kg and that exposuretime should be < 5 d to prevent liver, kidney, and cartilage damage. Based on these results, norfloxadin exhibitedpotential damage to the liver, kidney, and cartilage in Siberian sturgeon, suggesting that the dosing regimenmust be strictly followed in sturgeon aquaculture. Further study is needed to describe norfloxadin metabolism,residue, and damage repair. Suitable Chinese herbal medicines could be used to promote cartilage differentiationand repair.