This experiment explored the effects of fermentation time and temperature on polyphenol content in millet sour congee fermentation, and further compared the differences of main components between millet sour congee and millet congee. The results showed that the content of polyphenols in millet sour congee increased with time, and reached the maximum at 20 h. At the fermentation temperature of 32 ℃, the content of polyphenols in millet sour congee was the highest. Compared with millet congee, millet sour congee reduced the polyphenol loss caused by cooking, and the antioxidant activity of polyphenols in sour congee was higher than that of millet congee. The contents of protein and fat in millet sour congee were higher, reaching 13.5 mg/100 g and 6.2 mg/100 g respectively, while the starch content (53.4 mg/100 g) was 8.7 mg/ 100 g lower than that of Millet Congee. In addition, the fermentation of sour congee also increased the content of insoluble dietary fiber and the content of free tryptophan in the supernatant. This study provides theoretical support for further research and development of millet sour congee related dietary food.