A fluorometric method for the determination of F~-is developed.The fluorescence of calcein in pH=8.9 buffer solution can be quenched when the calcein reacts with Al~(3+).The complex of F~-and Al~(3+) is more stable than that of calcein-Al~(3+).When F~-reacts with calcein-Al~(3+),the fluorescence of calcein can be recovered.The changes of fluorescence has a linear relationship with the concentration of F~-in the range of 1.0×10~(-4)—1.0×10~(-3)mol/L.