In order to understand the formation mechanism of metabolites and the influencing factors of each link in the fermentation process of job's tears mash， the changes of metabolites in the fermentation process of job's tears mash were studied. The results showed that 49 small molecular metabolites were detected during the fermentation of job's tears mash， and their contents were significantly different （P<0.05）. There was little difference in the content of 17 free amino acids detected at the beginning of fermentation， only the content of threonine was slightly higher. After 24 hours of fermentation， the free amino acids began to increase significantly， and glucose and galactose also increased significantly. The changes of non-free fatty acids other than oleic acid and linoleic acid are not obvious. The content of unsaturated fatty acids such as oleic acid， linoleic acid， and 11-octadecenoic acid in free fatty acids is significantly reduced. The saturated fatty acids tend to increase， decrease， and increase. Microbial metabolism is the main cause of basic metabolic changes in the process of barley mash fermentation.