Abstract: [Objective] According to the first method in GB 5009.92-2016 Determination of Calcium in Food under National Food Safety Standard,the content of calcium in milk was determined by flame atomic absorption spectrometry and its uncertainty was evaluated. [Method] A mathematical model was established to analyze the source of uncertainty in the measurement process, quantify the evaluation, and calculate the synthetic relative standard uncertainty and extended uncertainty. [Result] When the confidence probability P is 95%, the extended uncertainty of calcium content is 3.22 mg/100g, that is, the determination result of calcium content in the milk is X=（123.80±3.22）mg/100g. [Conclusion]The main sources of uncertainty are the preparation of the standard working curve solution, the fitting of the standard working curve and the determination repeatability. The evaluation results of uncertainty can provide a reference for the accuracy of determination of calcium content in milk by flame atomic absorption spectrometry.

Key words: flame atomic absorption spectrometry, calcium, milk, uncertainty