Headspace-solid phase micro-extraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS) was applied to analyze the volatile compounds of the fresh adlay seeds and those with off-flavor. The results showed: more than 85 of volatile compounds which belonged to distinct chemical families were analyzed. A total of 47 compounds in fresh adlay seeds were identified (including 12 alcohols, 11 aldehydes and ketones and 22 hydrocarbons), the major volatile components in fresh adlay seeds were (+)-Limonene, benzene, 2-pentyl furan, hexanal, 1-nonanal, n-octanal, 2-heptanone, 1-pentanol, 1-hexanol, 1-octen-3-ol and linalool; While, there were 58 compounds in adlay seeds with off-flavor (including 17 hydrocarbons, 8 alcohols, 10 esters, 5 acids, 14 aldehydes and ketones), the major volatile components in adlay seeds with off-flavor were 1-pentadecene, hexanal, 1-nonanal, decanal, n-octanal, 1-octanol, hexanoic acid, heptanoic acid, octanoic acid and nonanoic acid. The main reason for the difference in the type and content of acid compounds in the main volatile components from fresh adlay seeds and those with 0ff-flavor may be the oxidation of fresh adlay seeds during storage.