Abstract: A RP-HPLC method with a fluorescence detector was established to determine enrofloxacin residues in eel or feed. The chromatographic conditions were: Waters Nova-Pak C18(3.9 mm i.d. ×150 mm, 4 μm)used for column(at 40℃)with 5mmol/L phosphate buffer (pH2.7)-acetonitrile(70:30,v/v)as mobile phase, flow rate 1.2 mL/min, the excitation wavelength of 280 nm and an emission wavelength of 450 nm. The detection limit for eel and feed was 1 μg/kg and 2 μg/kg respectively. The calibration graphs were linear from 30～500 ng/mL, and correlation coefficients r=0.9997. At the level of 10 μg/kg, 50 μg/kg and 100 μg/kg, the recoveries were 76%～98%,which are satisfactory as residues in trace test. RSD<8% meets the requirement too. This title specially introduced how to distinguish the false from the genuine.