Objective: To explore the correlation between BMI and gut microbiota of college students in Inner Mongolia,and to provide a reference basis for revealing the relationship between intestinal flora and obesity. Methods: Totally 88 college students from Inner Mongolia Medical University were enrolled, Height and weight were measured,and the feces samples were collected. The bacterial metagenome was extracted from dry feces samples for the concentration detection in per gram of dry feces,expressed as μg/μL. Correlation between BMI and metagenomics concentration of gut microbiota was statistically analyzed. Meanwhile,the metagenomics concentration of gut microbiota in different BMI groups was compared with each other. Results: There was a negative correlation between BMI and the metagenomics concentration of gut microbiota(r=-0.27,P<0.05). Significant difference in the concentration of gut microflora was observed between the normal group and the obesity group,the normal group and the overweight/obesity group(F=3.62,P<0.05). Among the female volunteers,there were significant differences between normal group and overweight group,between normal group and obesity group(F=1.87,P<0.05). No significant differences in metagenomics concentration of gut microbiota were found in different BMI groups(F=0.60, P>0.05). Conclusion There is a correlation between BMI and gut microbiota of college students in Inner Mongolia，the concentration of gut microflora metagenome in overweight and obese people decreased significantly.