Abstract: A reversed-phase high performance liquid chromatographic method with pre-column derivatization for the determination of alliin and it's related substances, which was the precursor of garlic's active component was established. Alliin was derivatized with 6-aminoquinolyl -N- Hydroxysuccinimicly Carbamate(AQC)，the reaction of derivatization was very fast and the derivative was stable . Analysis was carried out on a Kromasil C18 column（250mm×4.6mm，5mm）with a gradient elution at 248nm detector ,the mobile phase consisted of :(A):0.1% acetamide (0.03% acetic acid), (B) the mixture of water and acetonitrile（40：60）, The flow rate was 1.0ml/min, The linear calibration was found for alliin within the range of 1.1719-1500μg /ml （r=0.9998）,the within-day and between-day precision were good with RSD less than 1.8% (n=5), the recovery was 99.1% with the RSD of 1.9 %, the limit of detection was 3ng . the method established is accurate, simple and rapid and suitable both for assay and related substances test of alliin.