According to the national compulsory food safety standards National food safety standard -Determination of arsenic in food additives (GB 5009.76-2014), which was just fully implemented, the mathematical model for determination of arsenic content in food additives was introduced by investigating from the standard solution with the baking powder as a representative sample. The components of uncertainty in the detection process were classified and quantified, and were evaluated systematically. The combined uncertainty and the expanded uncertainty at 95% confidence intervals were obtained. Finally, the evaluation of uncertainty for determination of arsenic content in food additives by double channel hydridegeneration atomic fluorescence spectrometer was established. The experimental determination result was arsenic content 1.73±0.24mg/kg. The major uncertainty sources were the preparation of standard intermediate liquid and calibration working solution, curve fitting process and repeatability test.