【Objective】 To examine the epidemic of children's obesity in some areas of Shanghai and the relationship between demographic characteristics and children's obesity so as to provide the clues for preventing the obesity. 【Methods】 1 350 children from ten kindergartens were selected randomly from Hongkou district, Putuo and Pudong in Shanghai. A self-designed questionnaire was used to investigate the children's weight, height, and parenting characteristics, and so on. Children's height and weight came from the data of physical check in June, 2009. The relationships between demographic characteristics and children's obesity were analyzed with χ² test and multivariable logistic regression. 【Results】 The data showed that the rates of obesity and over-weight were 10.5% and 14.0% respectively. The place of registered residence, father's BMI, mother's BMI, children from only child family, and family structure were associated with obesity when other variables were not controlled. The father's BMI, mother's BMI, and family structure were associated with obesity when other variables were considered. 【Conclusions】 The rate of obesity and overweight in Shanghai is similar to that in developed countries. The main influence factor of child obesity in Shanghai is highly parents' BMI and nuclear family.