Abstract: The sample (0.100 g) was dissolved with 2 mL of hydrochloric acid, 0.4 mL of nitric acid and four drops of hydrofluoric acid by heating for 10 min. After cooling, the volume of the solution was made up to 50 mL in a plastic volumetric flask. The thallium in the solution was determined by graphite furnace atomic absorption spectrometry, at ashing temperature of 700℃, atomization temperature of 1 600℃, and 200 g·L^-1 tartaric acid was used as matrix modifier. Linear relationship between values of absorbance and mass concentration of thallium in definite ranges, with detection limit (3S/N) of 0.02 μg·L^-1. The determined results of the standard substances obtained by the proposed method were consistent with the certified values, and RSDs (n=6) were found in the range of 7.5%-9.9%.