Objective To explore the relationship between body mass index and dietary nutrition intake of middle school students. Methods Using stratified cluster sampling to select 1 000 middle school students in our city as the research object , of which 132 cases were over-recombination and 479 cases were the control group. Collect students’ basic information, dietary data and lifestyle information through questionnaire surveys, analyze and compare the energy and nutrient intake of the two groups of students ; use a multivariate Logistic regression model to analyze the relationship between children’s energy intake and dietary patterns and obesity. Results Among 1 000 middle school students, obese men accounted for 24.4%, women obese 23.5%, the gender difference was not significant (P>0.05); 11-13 years old obese accounted for 18.9%, 14-16 years old obese accounted for 29.0 %, the older the age, the higher the obesity rate (P＜0.05); the first grade obesity accounted for 9.0%, the second grade obesity accounted for 13.9%, and the third grade obesity accounted for 47.9%. The higher the grade, the higher the obesity rate (P＜0.05); the difference in age and height between the two groups of students was not significant (P>0.05). The weight, BMI, waist circumference, hip circumference, waist-to-hip ratio, diastolic blood pressure and body fat rate of the obese group (64.68±12.4kg, (27.54±2.46 ) kg/m2 , 98.43±9.14cm , 102.45±9.23cm, 0.98±0.08, 120.43±8.45mm Hg, 86.76±6.43mm Hg, (36.54±3.42)% are all compared with the normal group 42.56±8.45kg , (17.43±1.98) kg/m2, 69.43±7.5cm, 80.45±7.32cm, 0.86±0.08, 95.43±4.54 mm Hg, 67.43±4.32 mm Hg, (18.43±2.13)%the value is large (P＜0.05); the normal group students have energy, protein, fat/energy, carbohydrate, sodium, Iron intake 1765.59±345.79Kcal, 57.43±15.38g, (50.32±15.47) %, 128.43±29.43g, 1419.34±153.98mg, 14.54±4.21mg were all compared with the obese group (2361.56±354.78Kcal, 81.57±22.76g) , (90.43±15.23)%, 163.89±24.62g, 1587.43±123.32mg, 1.73±0.51mg) low (P＜0.05); the intake of energy, carbohydrates, protein, sodium and iron is positively correlated with the occurrence of obesity. Risk factors for obesity; and intake of vitamin C, vitamin E, potassium, calcium, and magnesium is negatively correlated with obesity and is a protective factor for obesity. Conclusion The overall weight control of middle school students in our city is not optimistic. Obese students have an imbalance in the intake of the three major nutrients and minerals, which will easily lead to obesity in the long run. The school and parents should work together to manage the student’s diet and exercise to ensure Student health.