Abstract: Uncertainties originated from the measurement of fipronil content in tea material by gas chromatography-mass spectrometry have been evaluated. The relative expanded uncertainty of the fipronil concentration was calculated to be 5.75% from the experimental data when the designed incredible probability was 95%(k=2). From the analysis of contribution rate which was calculated by different components combined to the combined uncertainty, the testing key issure for quality control was the uniformity and representative ness of samples and the precision of method.