Abstract: The characteristic mass spectra of chiral tertiary amine (Compound Ⅰ) and two kinds of quarternary ammonium salts derivated (compound Ⅱ,Ⅲ) were determined by gas chromatography electron ionization mass spectrometry (GC/EIMS). The molecular ion (M +) and quasimolecular ion (M+H +) was detected from compound Ⅰ, but only iodineloss ion (M I +) and bromineloss ion (M Br +) from compound Ⅱ, Ⅲ. The common fragementations m/z 241, m/z 209, m/z 88(base peak ion), m/z 77, m/z 58, m/z 45, m/z 44 and m/z 42 can be measured from compound Ⅰ, Ⅱ, Ⅲ. Their base peak ion m/z 88 can be used as symbol to go to the mass spectrometric analysis. The analysis of the fragemetation mechanism shows the privious cheracteristic mass spectra present because the molecular formula of chiral tertiary amine and quaternary ammonium salts derivated containe the dimethylamino.