Objective:The uncertainty of the determination of acid scarlet GR in orange juice by high performance liquid chromatography (HPLC) was evaluated. The source of uncertainty and the key factors affecting the test results were analyzed, so as to improve the accuracy of the test results.Methods:The mathematical model of uncertainty of acid scarlet GR content in orange juice was established. The factors that may introduce uncertainty in the detection process were analyzed, and the uncertainty components were evaluated.Results:The content of acid scarlet GR in self-made positive orange juice was 1.46 mg/kg, the expanded uncertainty was 0.11 mg/kg (including factork=2), and the determination result was expressed as:X=(1.46±0.11) mg/kg(k=2).Conclusion:This uncertainty mainly comes from the uncertainty introduced by the purity of reference materials, the linear fitting of standard curves and the analysis of high performance liquid chromatography.