Objective To evaluate the impact of a school-based intervention program to childhood obesity. Methods Eight middle schools (4 intervention and 4 control) were selected randomly from Huaiber urban district to attend the field trial. All the children (5 180 students, Grade 1 to 3) from these 8 schools were involved in the study and there were 2 346 cases in intervention schools (intervention group) and 2 834 cases in control schools (control group), respectively. Obesity was defined by WHO standard weight for height. The intervention group participated in a school-based intervention program over 3 school years (from 2000 to 2003). The program included dietary adjustment, sport prescription, health education, behavior corrects and stimulating acupuncture points in ears. Results 1. The prevalence of obesity among the children in the intervention group reduced from 9.8% to 7.0% over the 3 school years intervention periods, and it increased from 9.8% to 12.5% in the control group. 2. The degree of obesity among the children in the intervention group reduced from (45.9±11.83)% to (34.2±11.83)%(P0.05), while the degree of obesity among the children in the control group changed from (46.2±12.1)% to (48.9±13.7)%(P0.05). 3. The index signs such as TCH, TG, APOB and SBP all dropped after the intervention. Conclusions The school-based intervention for obese children can reduce prevalence of obesity and the degree of obesity significantly. [