Abstract: In an acetate buffer medium of pH 4.0,a sensitive fluorescence reaction was observed between Tl(Ⅲ) and morin,having its excitation and emission wavelengths at 426 nm and 489 nm respectively.Linear relationship was found between the intensity of enhancement of fluorescence (ΔF) and the concentration of Tl(Ⅲ) in the range 0.25-3.0 μg in 25 mL of solution.Precision of the method was tested at the concentration level of 2 μg of Tl(Ⅲ) per 25 mL of solution,and the value of RSD′s (n=7) obtained was 2.95%.Several simulated water samples were analyzed by the proposed method,values of recovery found were in the range 96.1%-102.2%.Separation of Tl(Ⅲ) from co-existing ions by the active carbon adsorption was adopted in the analysis.