The main nutrients needed for the growth of microorganisms in mouse feces were studied and the composition， structure and diversity of fecal microorganisms were analyzed. In this project， in vitro simulation combined with the addition of different prebiotics or nutrient elements were taken as the research method of study to explore the enrichment effect of these substances on microorganisms and the nutrients needed for microbial growth in mouse feces. This study demonstrated nitrogen source was a growth limiting factor for fecal microorganisms， other nutrients in MRS were not important limiting factors. In vitro culture of intestinal microorganisms found that nitrogen source alone was not suitable for enrichment of Lactobacillus intestinalis. But the addition of tryptone low poly fructose， the species richness and microbial biodiversity in mice were better than other groups which were the most suitable for in vitro screening of fecal microorganisms. The study of this project can provide good guidance for the application of probiotics and the screening of lactic acid bacteria.