Abstract: A method for determining 18 amino acids in tobacco flavors by liquid chromatography tandem mass spectrometry(LC-MS/MS) was developed.Using L-norvaline(Nva) as an internal standard,the sample was extracted by 10% methanol-water solution(HCl concentration of 0.1 mol/L),and the extract was directly analyzed by LC-MS/MS after filtering with a 0.22 μm aqueous phase filtration membrane.The results showed that:the linear correlation coefficients of 18 amino acids were above 0.9990 in the range of 0.1-10 μmol/L,and the recoveries of 3 standard addition levels ranged from 85.4% to 110.0% with the relative standard deviation(RSD) of 1.3%-4.9%.The limits of detection(LODs) and the limits of quantification(LOQs) of the method were 0.00005-0.1 µmol/L(S/N=3) and 0.0002-0.3 µmol/L(S/N=10),respectively.This method is accurate,sensitive and suitable for determining the amino acids in tobacco flavors.