The work aims to evaluate the uncertainty in determining the content of three antioxidants in plastic packaging materials by gas chromatography, and further improve the accuracy of the antioxidant detection data in plastic packaging materials. According to SN/T 3042—2011, the content of 3 antioxidants in plastic packaging materials was determined by gas chromatography. After analysis of factors affecting the uncertainty, the uncertainty of each main factor was calculated according to the corresponding mathematical model and the expanded uncertainty of the measurement results of 3 antioxidants in plastic packaging materials was obtained. The expanded uncertainty of measurement of three antioxidants in plastic packaging materials was BHA:(14.65±1.09)mg/kg, BHT:(14.68±1.03)mg/kg and TBHQ:(14.44±0.65)mg/kg (P=95%, k=2). The main factors affecting the determination uncertainty of the content of three antioxidants in plastic packaging materials by gas chromatography are:standard curve fitting, measuring tool for preparing standard working fluid and instrument precision. The uncertainty can be reduced by more accurate measuring tools and instruments, suitable concentration points of standard working fluid, and improved practical level of personnel, so as to further improve the accuracy of detection data.