Abstract: Objective To ivestigate the status and influencing factors of overweight and obesity among middle school students in Maanshan city.Methods 4607 students in 10 middle schools were randomly selected from Maanshan using cluster sampling.Epidemiological investigation and anthropometric measurement were jointly carried out.Results The prevalence rate of overweight and obesity was 10.2% and 3.8%,respectively.The prevalence rate of over weight in the male was significant higher than that of in the female(χ²=55.396,P<0.05),so did the prevalence rate of obesity(χ²=20.830,P<0.05).The prevalence rate of overw eight in 13~15 age group was higher than that of in 16~18 age group.The prevalence of over weight and obesity among students in city was higher than that of in outskirts and small town.There was a significant difference in the prevalence of overweig ht between outskirts and small town,but no difference was found in the prev alence of obesity.Conclusion The prevalence of overweight and obesity among middle school students in the city was very high,and significantly associated with demography features such as sexe,age,living area,education of parents.