Abstract: The measurement of trace mercury in silicates is of great significance to the determination of mercury content in rocks and study of theoretical geochemistry, exploration geochemistry, and ecological and environmental geochemistry. However, the distribution of mercury in silicates is in trace level, which demands high criterion to the detection limits of analytical methods. The accurate measurement of trace mercury in silicates also faces challenges such as the great variation of silicon dioxide contents in silicates, multiple lithology classification, complex interference matrix composition, and element volatilization loss. The direct sampling mercury analyzer, without chemical digestion process (to prevent mercury volatilization loss), using catalytic tubes (to eliminate complex matrix interference) and mercury trapping devices (to reduce the detection limit by enriched element), can provide a solution in line with the development trend of green chemistry technology. In this study, the parameters of direct sampling mercury analyzer are optimized through experiments. The method indicators, including detection limit (0.5×10^-9), determination lower limit (2.0×10^-9), accuracy (ΔlogC < 0.05) and precision (RSD < 10%, n=12), meet the requirements of Specification of Multi-Target Geochemical Survey in DZ/T 0130-2006, and reach or excel the detection limit (2×10^-9) and quantitative lower limit(5×10^-9) in GB/T 14506.33-2019 Methods for Petrochemical Analysis of Silicates(Determination of Mercury Content: Hydride Generation-Atomic Fluorescence Spectrometry), which can provide references for determination of trace mercury in silicate samples by atomic fluorescence spectrometry and improvement of green chemistry technology.