Objective To explore the relationship between body mass index(BMI),and blood pressure in overweight and obesity children.Methods Body weight,height and blood pressure were measured in 2 566 school children(12~15 years of age)..Results The prevalence of high status of blood pressure in 2 566 school children is 20.7%,among which the prevalence of high status of blood pressure is 19.15% in the normal weight children,34.55% in overweight children and 39.29% in obese children.There was significant difference in the prevalence of high status of blood pressure among normal weight children,overweight and obesity.Conclusion The morbidity of high status of blood pressure increased obviously with the increase of BMI in school children.