【Objective】 To study the association of mothers' weight gain during pregnancy and infants' early feeding mode on children' obesity so as to provide the clues for preventing the children's obesity. 【Methods】 A total of 949 children from four second-level kindergartens were selected randomly from two communities in Hongkou district in Shanghai. A self-designed questionnaire was used to investigate the children's weight, height, family conditions, the mothers'weight gain during pregnancy and infants' feeding mode,and so on. The relationship between the mothers' weihgt during the pregnancy, infants's feeding mode and children's obesity were analyzed with χ² test and binary logistic regression. 【Results】 Resulst of the study showed that the rates of obesity and over-weight was 10.1% and 13.2% respectively. Pregnancy weight gain ≥ 15 kg, children exclusively breastfed within 6 months were associated with obesity when age, gender, the characteristic of registered residence,family structure and family income were considered. 【Conclusions】 Mother's weight gain more than 15 kg during pregnancy may be a risk factor for childhood obesity; And exclusive breastfeeding within 6 months may be a protective factor on children's obesity which may reduce the incidence of obesity in children.