A high performance liquid chromatography ( RT-HPLC) method for detection of chloramphenicol ( CAP) in the plasma of nile tilapia ( Oreochomia niloticus) was described and the effect of different water temperatures ( 18e and 26e ) and age of fish ( 1 year old and 2 years old) on the pharmacokinetics of CAP in nile tilapia after oral administration at a single dosage of 50 mg#kg - 1 body weight was examined in this study . The results showed that with RT-HPLC base line was smooth and the object peak of the drug was utterly separated from the impurity . The method was validated with blank samples fortified at 0. 25, 2. 5, 12. 5 Lg#mL- 1, and the mean recovery rate of CAP in plasma was ( 90. 47? 3. 42)% and the co efficient of variation was below 10%. The average intraday precision and inter- day precision were perfected, and the coefficient of variation were 1. 199% and 1. 770%, respectively. The pharmacokinetics of CAP had some relationship with water temperature and age. With the rise of water temperature, the speed of absorption, distribution and elimination of CAP in plasma accelerated. Not only the half- time of absorption ( T1/ 2kA) of the 26e group was about one third that of the 18 e gro up, but also the half-time of distribution ( T1/2A) and the half- time of elimination ( T1/ 2B) less than those in the 18e group. The time to peak concentration ( Tp) of the 26e group was less than half that in the 18e group, and the body clearance ( CLs) of the 26e gro up was about 1. 74 times greater than that in the 18e group, indicating that CAP was more rapidly cleared in higher water temperature. The speed of absorption in the 1 year old group was significantly higher than that in the 2years old gro up, and Tmax in the 1 year old group was significantly shorter than that in the 2 years old group, but T1/ 2kA and the area under concentration ( AUC) in the 1 year old gro up were close to that in the elder gro up. The speed of absorption in one years old group was much higher than that in tw o years old group, however, the speed of elimination of the former was much slower than that of the latter. Therefore, in view of the toxicity of CAP, it is important to be concerned about the pollution of CAP in aquatic animal food, and more attention should be paid to aquatic animals with relatively small age those live in relatively low water temperature in order to assure safety of aquatic food product.