120 volunteers were randomly divided into three groups: high fat diet group, high sugar diet group and high fiber diet group. The changes of intestinal microflora were analyzed, DNA was extracted, PCR amplification and product purification were carried out, and biological indexes were tested. The effects of high-fat diet on intestinal microbial metabolism were studied. It was found that high-fat diet could increase body mass and promote intestinal harmful microbial metabolism. The diversity of intestinal microorganisms in the experimental group was higher than that in the control group. To study the effect of high-sugar diet on intestinal microbial metabolism, it was found that the body weight of the subjects in the experimental group was significantly higher than that of the control group, and the high-sugar diet structure could increase the blood glucose level. The intestinal microbial diversity of the control group was higher than that of the experimental group, and the content of sclerenchyma in the experimental group was significantly higher than that of the control group, while the bacteroides was significantly lower than that of control group. To study the effect of high fiber diet on intestinal microbial metabolism, there was no significant difference in richness, Shannon index and homogeneity between high fiber control group and experimental group. There was no significant change in the number of bacteria. It was concluded that high-fat and high-sugar diet structure could promote the metabolism of harmful microorganisms and high-fiber diet structure could promote the metabolism of beneficial microorganisms.