The volatile compounds formation from the complex Maillard three-component reaction system， L-ascorbic acid-L-cysteine-glycine (ASA-Cys-Gly)， was investigated under different pH (ranging of 4.5， 5.8， 7.0， 8.0， 9.5) conditions. The headspace solid-phase micro extraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) technology， internal standard and standard material were used to analyze and identify the volatile substances in each reaction system. Meanwhile， the effect of pH on the formation of volatile in the three components complex Maillard system was explored based on research of the volatile generation and distribution in the self-degradation and the two components reaction system. The results showed that the volatile compounds generated from the three components complex Maillard reaction system were various organic substances， such as thiophene， thiazole， pyrazine and mercaptans. There were many kinds of thiophenes with high concentration under acidic and alkaline conditions， which were the dominant product in that reaction system. However， thiazole and pyrazine were major produces under medium alkaline conditions. Mercaptans were mainly generated under acidic conditions. According to the formation and distribution of volatile substances in each system， the possible generation mechanisms of volatile substances under different pH conditions were proposed.