This experiment established an evaluation method for the uncertainty in the determination of malondialdehyde in oils using high-performance liquid chromatography according to GB 5009.181-2016"National Standard for food safety Determination of malondialdehyde in food"for testing,and according to JJF 1059.1-2012"evaluation and expression of measurement uncertainty",comprehensive analysis was conducted on the sources of various uncertainty factors during the experimental process.Established a mathematical model for the uncertainty of malondialdehyde content in oils and fats.The results showed that the uncertainty was mainly caused by the preparation of reference materials(accounting for approximately 82.23%),and the second is the fitting of the standard curve(accounting for approximately 8.61%).Therefore,the High-performance liquid chromatography should be maintained regularly in daily work and select a glass measuring instrument with high accuracy for standard solution preparation.