Abstract： Objective To determine the relationship between birth weight,gestational age at birth,intrauterine nutritional status and childhood obesity.Methods Physical examinations of 2395 6 to 10-year-old children were performed,and questionnaire survey was used to collect their birth data.The relationship between birth weight,gestational age at birth and childhood obesity was analyzed.Results The risk of childhood obesity for macrosomia at birth (birth weight≥4000 g) was 1.55 times as much as that of children with normal birth weight (OR= 1.55,95%CI:1.17-2.05,x2 =9.380,P=0.002),and the risk of obesity for large for gestational age (LGA) babies was 1.38 times as much as that of appropriate for gestational age babies (AGA) (OR= 1.38,95%CI:1.05-1.82,x2=5.206,P=0.023).Compared with the normal term infants,the rate of obesity in preterm infants and postdated child increased,but there was no statistical difference (OR= 1.38,95 CI:0.82-2.3,x2 = 1.448,P= 0.229;OR= 1.34,95%CI:0.71-2.51,x2=0.834,P=0.361).Conclusions Macrosomia and LGA are the risk factors for childhood obesity.