Abstract: A method for the determination of micro-amount of mercury in sulfur samples was developed. The samples were digested in closed-vessel and micro-amount of mercury in sample solution was determined by atomic fluorescence spectrometry. The digestion experiments were designed using orthogonal test. In the closed system, the complete digestion of the sample was performed using concentrated nitric acid and hydrogen peroxide. The effects of acidity of the medium and the amounts of KBH4 on sample digestion were studied and the operating conditions of the instrument were optimized. The detection limit (3σ) of Hg was 0.0127 ng/mL and the recovery is 98.0%～104.0% with the precision of 2.00%～4.74%RSD (n=11). The method has been applied to the determination of microamount of mercury in foodstuff and industrial sulfur samples with advantages of high sensitivity, precision and accuracy, simple operation and less environmental contamination risks.