Abstract: Florfenicol, the latest generation chloramphenicols, has been specifically developed for veterinary use. Tilapia is a very important cultured fish species in China. Therefore the studies on pharmacokinetics of florfenicol in tilapia will be very helpful to guide the use of the drug. The pharmacokinetics of florfenicol was studied in plasma of tilapia (Oreochromis niloticus O. aureus) in freshwater at 22℃. The fish weighing about 98 g were forced-fed with medicated feed containing a single dose of 10 mgkg-1 bodyweight of florfenicol. The pharmacokinetic data derived from the experiment were analyzed by non-compartmental methods based on statistical moment theory. The peak drug concentrations (Cmax) in plasma and muscle were estimated to be 4.46 gmL-1 and 6.88 gg-1, respectively, and the time to the peak drug concentration (Tmax) in both plasma and muscle was 12 h. And correspondingly the elimination half-lives during elimination phase (T1/2) were 10.03 h in plasma and 10.97 h in muscle. The drug concentrations in both plasma and muscle maintained above the effective concentrations (MIC0.8 gmL-1) beyond 40 h following a single oral dose of 10 mg florfenicolkg-1, and at 168 h after administration, the drug level, was 0.04 gmL-1 in plasma and was below detection limit (0.03 gg-1) in muscle, which indicated florfenicol was effective against pathogens and rapidly eliminated, resulted in low residue in tilapia, so it was safe to be used. Therefore, florfenicol was of great value for the control of bacterial diseases in fish.