Abstract: The method of the determination of 2-methylimidazole and 4-methylimidazole in vinegar by selected ion GC-MS was established. The chromatographic conditions were selected and optimized. The sample were first alkalized, purified by kieselguhr, eluted with dichloromethane. The eluate was combined and concentrated, then with N-methyl-formanilide as internal standard, volumed to the 10mL volumetric flask with dichloromethane, then determinated by GC. The results showed that the concentration of 2- methylimidazole and 4-methylimidazole both in the range of 0 ¹5.2mg/L had good linear relationship. The correlation coefficients respectively were 0.9997 and 0.9996;the relative standard deviation were respectively 3.0% and 3.1%. The average recoveries of 2-methylimidazole and 4-methylimidazole were 101.3% and 99.3%. This method was used to determine 2- methylimidazole and 4- methylimidazole in commercial vinegar, and the satisfactory results was achieved.