Abstract: A surface desorption atomospheric pressure chemical ionization mass spectrometry(SDAPCI-MS) method was employed to directly fingerprint 3 condiment vegetables including leek,onion,garlic with neither sample pre-treatment nor toxic chemical contamination.Identification of the molecular structure of desired ions was demonstrated by tandem mass spectrometry(MS/MS).The results show that the main components in chemical fingerprint spectrum of leek are 2-methyl-2-pentenal,methyl methanethiosulfinate,methyl allylthiosulfinate etc.,among which both methyl methanethiosulfinate and methyl allylthiosulfinate give a relatively strong signal of M+H₂O^·+. Intact onion bulb shows so few signals in the mass spectrum that only initial ions caused by corona discharge,such as H₃O⁺(OH),and O₂⁺,are detected.On the other hand,dissected onion bulb gives contrastively increased mass spectrum signals,namely,S-propentyl sulphinate,propyl allylthiosulfinate and propyl propylthiosulfinate.While allyl allylthiosulfinate is detected as the main volatiles of intact garlic bulb,dissected garlic bulb mainly gives S-propentyl sulphinate.Some other signals of interested,such as methyl methanethiosulfinate,methyl allylthiosulfinate from leek,S-propentyl sulphinate from onion and allyl allylthiosulfinate from garlic were structurally identified by tandem mass spectrometry(MS/MS).As the experimental findings shows,SDAPCI-MS technique is qualified for rapid non invasive analysis without sample manipulation prior to experiment,and provides practical and potential application in non-destructive testing and quality control for food.