Abstract: The change of chemical compositions of coix seed vinegar such as acetic acid, flavonoid, polyphenol, polysaccharide, amino acid nitrogen, coixol and organic acid were analyzed during primary fermentation and aging process.The study aimed to provid theoretical guidance for the coix seed vinegar production technology improve. The results showed that: the acetic acid and amino acid nitrogen content of coix seed vinegar gradually increased throughout the fermentation stage and eventually stays stable.Flavonoid content was decreased at first and then increased in the main fermentation stage which was the same as polyphenol content change, flavonoid content reached a minimum as 105.38mg /L after main fermentation 4d.Both of flavonoid and polyphenol content showed a slow increased in the aging stage.The polysaccharide content showed a declined but fluctuations trend.The coixol content was showed the change trend of “high- low”.The organic acid content was increased in the entire fermentation phase but decreased in the aging stage.The quality indicators of product performed well after aging.