Objective:The uncertainty of determination of Isocarbophos residues in tea by using QuEChERS-gas chromatography-tandem mass spectrometry techniqne was evaluated. Methods:Isocarbophos residues in tea was determined by using "GB 23200.113—2018 National food safety Standard-Determination of 208 pesticides and metabolites residues in plant origin-Gas chromatography-tandem mass spectrometry method", and factors in the determination of isocarbophos were analyzed by establishing a mathematical model, including sample weighing, volume, calibration of standard solutions, repeatability and recovery rate, etc.. Results:When the residual amount of isocarbophos in tea was 0.050 mg/kg, the expanded uncertainty was 0.007 mg/kg, and the determination result was expressed as:ω=(0.050±0.007) mg/kg,k=2. Conclusion:The main sources of uncertainty in this method werecalibration of standard solutions and the recovery rate.