Abstract: The amount of residual triazophos in green tea was determined by gas chromatography tandem mass spectrometry (GC-MS/MS) and then the uncertainty was evaluated. According to ISO/IEC Guide 98-3: 2008 (GUM method) and GB/T 27411-2012 "Common uncertainty assessment methods and representations in testing laboratories" (control chart method), the uncertainty of the measurement results was analyzed and quantified. Results showed that, the evaluation results of the GUM method and the control chart method were (0.112±0.012) mg/kg, k=2 and (0.108±0.018) mg/kg, k=2, respectively. The main sources of uncertainty of the GUM method were mass concentration and instrument stability, which accounted for 38.9% and 24.7% of the total uncertainty respectively. The control chart method only performed statistical analysis of the test results, which was simple and easy to operate. It inspected the long-term trend of the test results and could be implemented in the application of internal quality control in daily testing work. The GUM method was suitable for re-examination of samples or the evaluation of uncertainty requirements by customers. The calculation was complex, but the uncertainty evaluation results could be obtained in the short term.