Based on GB 23200.92-2016, the samples were detected, and a mathematical model was established. Moreover, each uncertainty of the whole analysis procedures was analyzed and quantified. It was found that, when the pentachlorophenol residue was 14 μg/kg, the extended uncertainty was 3 μg/kg (k=2) under the 95% confidence interval. The results showed that the main sources of measurement uncertainties are derived from the final volume of sample, measurement repeatability, standard solution preparation, and the calibration fitting.