Abstract: Objective To assess the prevalence of overweight/obesity,and its association with sleep duration and physical activities,so as to provide evidences for weight management.Methods Cluster sampling method was employed to select 3 020 students from middle and high schools from Shenzhen,Yangjiang,Qingyuan in Guangdong Province to participate a school-based cross-sectional study with self-reported questionnaires on sleep duration,exercise.And they were investigated about weight and height to analyze their BMI.Results The prevalence of overweight/obesity was 11.49% (13.18% in junior school students,9.54 % in senior school students),about 94.23% of the senior school students obtain less than 8 hours of sleep per day,while 74.83% of the junior school student gets less than 8 hours of daily sleep;The rate of participation of adequate high intensity exercise and small intensity exercise were 32.61% and 29.02% among junior school students,while 18.52% and 18.87% among senior schoolstudents.The differences were of statistical significance(P<0.05).Univariate analysis showed that the prevalence rate of obesity/obesity was higher among those who sleep less than 8 hour a day than those who sleep enough among senior high school students.Multivariate analysis showed that after adjusting for socio-demographic variables,physical activity and gender,the odds ratio (OR) for overweight/obesity comparing sleeping <8 hours with ≥ 8 hours was 2.77 (95%CI=1.34-5.75) among senior school student.There was no significant association between physical activity and overweight/obesity in adolescents.Conclusion Short of sleep is the single risk factor of overweight and obesity among senior school students,while physical activity may not associated with overweight and obesity among junior and senior school students.