Abstract: According to the second part of NY/T761—2008, the vinclozolin residue in cucumber was determined by GC. The sources of uncertainty components coming from the measuring process was analyzed. The mathematical model for the evaluation of measurement uncertainty was built and the uncertainty components were synthesized and expanded. The results showed that the relative combined standard uncertainty and expanded uncertainty of measurement results were 2.78% and 5.56% (k=2), respectively. The sources of measurement uncertainty mainly derived from diffusion and constant volume process of standard solution, the recovery rate in the extraction and purification process, and the error caused by the measurement of chromatographic peak area. The results of this study provide a reference for objective evaluation of the pesticide residue detemanation results.