Objective: Uncertainty assessment of the content of synthetic capsaicin, natural capsaicin and dihydrocapsaicin in edible oils and fats by liquid chromatography-mass spectrometry was carried out, and the sources of uncertainty and the key factors affecting the test results were analyzed, so as to improve the accuracy of test results.Methods: To establish a mathematical model for the uncertainty of the content of synthetic capsaicin, natural capsaicin and dihydrocapsaicin in edible oils and fats, to analyze the factors that may introduce uncertainty in the detection process, and to evaluate each uncertainty component.Results: The contents of synthetic capsaicin, natural capsaicin and dihydrocapsaicin in edible oil were (0.250±0.032), (0.123±0.015), (0.130±0.014) μg/kg,k=2.Conclusion: This uncertainty is mainly derived from the linear fitting of the standard curve and the uncertainty introduced by the analysis of liquid chromatography-mass spectrometry.