Abstract: Objective To explore the association between birth weight and obesity in children,and to provide references for making preventive measures for the high-risk children of obesity.Methods A total of 1 574 children aged 7-11 years from 12 primary schools in Dongcheng district of Beijing were selected to have a physical examinationincluded in the study.The data of Their their body weight and height was measured to calculate the body mass index.Questionnaires were used to collect relevant information including birth weight,screen-based sedentary behaviors,moderate to vigorous physical activity and dietary status.Logistic regression model was employed to analyze the association between birth weight and obesity after adjustment of other potential risk factors.Results The total prevalence of overweight and obesity in normal birth weight group,low birth weight group and macrosomia group were 31.99%,27.03% and 46.33%,respectively.The prevalence of obesity were 17.43%,21.62% and 28.81% in the three groups(x2 =15.17,13.50,P<0.01).Logistic models showed that the risk of obesity during childhood in macrosomia group was 1.76 times higher than that in normal birth weight group(95%CI=1.17-2.67).The difference of obesity prevalence during childhood between low birth weight group and normal birth weight group was not statistically significant(OR=1.45,95%CI=0.56-3.75).Conclusion Macrosomia is independently associated with childhood obesity.In addition to the diet,behavior,genetic factors,the childhood obesity in the early stage should also be focused on to prevent the childhood obesity.