Abstract: A gas chromatography-mass spectrometric (GC-MS) method was developed for the determination of methyl aniline compounds (including N-methyl aniline, p-methyl aniline, o-methyl aniline, m-methyl aniline, N,N-dimethyl aniline) in gasoline. The methyl aniline compounds were liquid-liquid extracted with acid and separated by capillary chromatographic column, the qualitative measurements were conducted with selected ion monitoring mode（m/z=107, 120）and then quantified with external standard method. The concentration of extractant in sample pretreatment and the type of capillary column used were optimized. It is concluded that using hydrochloric acid solution with volume fraction of 10% as extractant, separating by DB-1MS (30 m×0.25 mm×0.25 μm) capillary column, with methyl aniline compounds concentration in the range of 100—300 mg/L, the recoveries of standard addition are in the range of 85%—103%. The relative standard deviations of reproducibility tests are not more than 2.5% and the detection limit is 1.0 mg/L when SNR (signal to noise ratio) is established as 3. This method is accurate, with good reproducibility and low detection limit.