Objective To investigate and analyse the incidence rate and body constitution of obese children in Ji'an city. Methods Investigation was conducted in three primary schools in Ji'an city.The body height and weight of children enrolled were measured uniformly and strictly using the same height measuring gauge and weighing scale.The incidence rate of obese children was calculated.The body constitution including cardio-pulmonary function and physique of all children was measured and compared.All children's behavior and life styles were investigated by questionnaires. Results The incidence rate of children obese was 8.68% in Ji'an city,9.50% of boys and 7.78% of girls respectively.The body constitution was worse in obese children than normal children besides vital capacity.The ratios of tachyphagia,snacks and meat preference,low amount of exercise were significantly higher in obese children than normal children. Conclusion The incidence rate of obese children is high in Ji'an city and the body constitution is worse in obese children than normal children.The obesity in children is related to certain behavior and life styles.