Abstract: The sample (about 0.1 g) was ultrasonically extracted with about 6 mL of n-heptane for 15 min, and the mixture was let stand for cooling, and then made up to 10.0 mL with n-heptane. After the mixture was mixed well and let stand for several minutes, the supernatant was taken and filtrated with 0.22 μm organic filter membrane. An Agilent HP-INNOWax capillary column (30 m×0.25 mm, 0.25 μm) was used for separation, and electron bombardment ion source and multi-reaction monitoring mode were selected in mass spectrometry. The peak area of 3-acetyl-2,5-dimethylthiophene was kept linear with its mass concentration in the range of 0.010-2.00 mg·L^-1, and the detection limit (3S/N) was 0.1 mg·kg^-1. Tests for recovery obtained by standard addition mehtod was carried out with the thin paste flavor samples as the matrix, giviny results in the range of 82.7%-92.9%, and the relative standard deviation (n=6) of the measured values were between 0.70% and 2.8%. Values of recovery was between 92.2% and 107%, with different types of flavor samples as the matrix.