To evaluate the uncertainty of the determination of sibutramine content in health foods by liquid chromatography-tandem mass spectrometry. Methods according to BJS 201701 Determination of sibutramine in food,and the content of sibutramine in health foods was detected. According to the approach in measurement uncertainty and results indication(JJF 1059.1 2012), the uncertainty was analyzed, quantified and synthesized. When sibutramine content was 7.04 μg/g,the extended uncertainty was 0.197 μg/g (k=2) under the 95% confidence interval. The main influence factors of the uncertainties in the determination were standard curve fitting process.