Coarse cereals intake can reduce the incidence of some chronic metabolic diseases. However, there is no uniform standard for coarse cereals intake, and unknown whether high coarse cereals intakes have adverse effect on health remains. In this study, 3-week-old C57BL/6J mice were intervened by adding different ratios of foxtail millet in feed, including 20%, 40%, 60%, and 80% additions for 12 weeks. Using the automatic biochemical analyzer, high-throughput sequencing of 16S rRNA gene, gas chromatography mass spectrometry, the effects of different ratios of foxtail millet on lipid blood levels, gut microbiota and short-chain fatty acids in mice were analyzed. The results showed that the feed with 80% supplementation foxtail millet significantly increased the total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, propionic acid, butyric acid, isobutyric acid and valeric acid. In addition, foxtail millet intake increased the abundance of Bacteroidota and Muribaculaceae, decreased the abundance of Firmicutes, Actinobacteriota, Lactobacillaceae and Bifidobacterium. The gut microbiota composition in mice varied with different levels of foxtail millet. The microbiota of mice fed with the supplementation of 20% were enriched in Alistipes, Parabacteroides, Enterorhabdus. However, the abundances of Faecalibaculum, Blautia and Roseburia were reduced for the mice fed with the supplementation of 80%. The results showed that, 20% intake of foxtail millet was sufficient to regulate gut microbiota, while 80% intake led to abnormally elevated lipid levels in blood, reduced the diversity and evenness of gut microbiota, and decreased the abundance of probiotics. Therefore, coarse cereals' nutritional value should be rational considered and excessive intake patterns for coarse cereals should be avoided.