The possible uncertainties in the determination of No.6 solvent residual in vegetable oil by headspace gas chromatography and ultrsonic vibration-headspace gas chromatography were analyzed and evaluated. According to Evaluation and Expression of Uncertainty in Measurement (JJF 1059.1—2012) and Guidance on Evaluating the Uncertainty in Chemical Analysis (CNAS-GL06), a mathematical model of uncertainty was established. To quantify each component, the results showed that the key influence factor of uncertainty of test was the pretreatment of samples and its standard curve.