Abstract: A method for continuous determination of trace Ag, Cd and Tl in geochemical samples by flame atomic absorption spectrophotometry with KIMIBK extraction was developed. The sensitivity and signal stability for these elements were remarkably improved by modification of gas control system and nebulizer of flame atomic absorption spectrophotometer. The extraction condition was also optimized with 1.2 mol/L HCl extraction system and phase ratio (A/O) of 3∶1~4∶1. At the optimum conditions the detection limits (3s) were 0.004 μg/g for Ag, 0.007 μg/g for Cd and 0.011 μg/g for Tl. The precisions (RSD,n=12) of the method for Ag, Cd and Tl were 4.5%～9.6%, 1.5%～7.9% and 4.5%～5.4% respectively. The method has been applied to the determination of these elements in internal control samples and National Standard Reference Materials with satisfactory results.