Objective: To understand the prevalence of obesity and its associations with diet,exercise and mental health among students in Inner Mongolia, so as to provide scientific basis for the formulation of obesity intervention measures for students in this area. Methods: Stratified and cluster random sampling was used to select 186 649 students from all 12 cities and 103 banners and counties in Inner Mongolia Autonomous region. All the participants were divided into groups according to the BMI classification criteria for overweight/obesity screening of Chinese school age children and adolescents (kg/m 2). Univariate analysis was carried out by means of rectangular χ 2 test, and multivariate unconditional Logistic regression model was used to screen the risk factors of obesity. Results: The overall obesity rate was 18.54%, the obesity rate of boys was 22.04 %, and the obesity rate of girls was 14.99%. The results of multivariate Logistic regression analysis showed that area(OR=0.79), sex (OR=0.61), times of eating fried food per day (OR=1.08), daily exercise for more than 60 minutes per week >2 days (OR=0.89),eat breakfast every day (OR=0.86), times of drinking drinks per day (OR=1.12), Smoking (OR=0.87), drinking (OR=1.07), eating fruit per day (OR=1.07), watching TV ≥2 hours a day (OR=1.06), sleeping time (OR=0.93) and school period may be related to obesity (P<0.05). Conclusion The overall obesity rate of students in Inner Mongolia is relatively high, and the occurrence of obesity is related to diet, exercise behavior, living habits and psychological factors.