Abstract: The founder Paralichthys olivaceus were divided into three groups randomly and the pharmacokinetics and bioavailability of danofloxacin were examined in healthy and Vibrio anguillarum infected founder Paralichthys olivaceus. Concentrations of dano floxacin were determined by the High Performance Liquid Chromatography and data were analyzed with the pharmacokinetic computer program MCP-KP. The results showed that blood concentration of danofloxacin in healthy P. olivaceus after intravascular administration (5 mg·kg^-1 body weight) was described by a one-compartment open model with no absorption. The blood concentration-time curves after oral administration (10 mg·kg^-1 body weight) in healthy and infected P. olivaceus all could be described by a one-compartment open model with the first order absorption; whereas the liver and kidney were both fit to the two-compartmental open model with the first order absorption. Compared with the healthy P. olivaceus the pharmacokinetic parameters of danofloxacin in infected founder had great changes, such as the area under concentration-time curve decreased from 256.07 mg·h^-1·L^-1 to 209.18 mg·h^-1·L^-1,the maximum drug concentration decreased from 5.699 μg·mL^-1 to 2.932 μg·mL^-1, the elimination half-life increased from 27.758 h to 46.195 h, and the bioavailability was 71.21% for healthy fish and 58.17% for infected fish.