Using reversed phase high performance liquid chromatography(RPHPLC), the pharmacokinetic differences of difloxacin(DIF) with a single dose of 20 mg/kg body weight after oral administration were compared in crucian carp （Carassais auratus gibebio） at the water temperatures of 16 ℃and 25 ℃.Analyzed with Practical Pharmacokinetics Program (3P97)，the results show that the kinetic profiles of DIF，which have significant differences within the two grades temperature, conformed to a twocompartment model, and the absorption halftimes(T_1/2Ka) were 0.009 9 h and 0.122 2 h at 16 ℃and 25 ℃, which were found to have a positive relationship with water temperature, while the elimination halftimes（T_1/2Ka: 70.968 and 18.322 h）,the apparent distribution volumes（Vd/F: 1.875/kg and 0.676/kg）,the area under the concentrationtime curves ［AUC,μg/(mL·h)］ of plasma (763.761 and 243.244) and tissues (746.622，1 095.711，1 222.75and 294.857，258.587，344.63 in liver, kidney and muscle ,respectively) have negative relationships with water temperature. Besides the metabolite of DIF, sarafloxacin (SAR), all can be detected in the plasma and tissues(liver, kidney and muscle) at 16 ℃and 25 ℃, whose kinetic profiles have multimodal phenomenon. The results indicate that the distribution of DIF at 16 ℃ is wider than that at 25 ℃. In addition, the time, when ratio of C_max/MIC₉₀≥10 was greater than or equal to 10 at 16 ℃,could reach 72 h，while it was 4-6 h at 25 ℃;Therefore, DIF may have higher efficacy at low water temperature(16 ℃).