In the present study, the alliin and methiin as the precursor of the primary functional active components in garlic were tested by using Fourier transform infrared (FT-IR) spectroscopy and confocal micro-Raman spectroscopy. Significant IR and Raman absorption peaks were detected in the range of 3　200～2　800 cm-1 and 1　700～200 cm-1, respectively. For alliin eight intense IR absorption peaks were observed at 3　080, 1　617, 1　582, 1　496, 1　418, 1　342, 1　301 and 919 cm-1, respectively, and nine strong Raman vibration peaks were assigned at 3　088, 1　636, 1　404, 1　290, 1　051, 790, 745, 693 and 588 cm-1, respectively, as its characteristic peaks. In parallel, for methiin eight strong IR absorption peaks were revealed at 1　644, 1　481, 1　395, 1　370, 1　233, 1　068, 1　004 and 892 cm-1, respectively, and nine intensive Raman vibration peaks were presented at 1　644, 1　310, 1　073, 1　011, 998, 893, 846, 702 and 676 cm-1, respectively, as its characteristic peaks. It is concluded that the IR and Raman spectra of alliin and its homologue, methiin, show obvious differences, and these two methods are provided for the rapid and simple analysis of alliin and its homologues.