Abstract: A new fluoremetric method for determination of nitrite in nitric acid medium was studied, based on the reaction of nitrite and 5-aminofluorescein in nitric acid medium to form a new compound which has no fluorescence, then reduced to high fluorescence in alkaline medium, thus the concentration of the nitrite can be determined by detecting the intensity of fluorescence. The method precision is better than 7% (relative standard deviation of the measurements), with an uncertainty of 13％ at the 95% confidence level, and the detection limit is 7×10^-5 mol/L. The recovery ranges from 89% to 104%. This technique is characterized with high sensitivity, easy operation and low interference effects. It can be used for detecting nitrite directly in nuclear fuel reprocessing feed solution.