Objective： To explore the association of physical activities, sedentary behaviors with overweight/obesity in Chinese children aged 9-11 years, analyze the gender difference and heterogeneity of the association across different provinces, and provide evidence for prevention and control of overweight and obesity. Methods: Using the data of 40 692 children aged 9-11 years from Chinese National Survey on Students’ Constitution and Health in 2010, the height and weight were measured and the time spent in physical activities, screen behaviors and homework were collected. We analyzed the associations among physical activities, sedentary behaviors and overweight/obesity in boys and girls separately, and assessed the heterogeneity of associations across different provinces with Meta-analysis. Results: The prevalence of overweight/obesity of the boys (27.1%) was higher than that of the girls (12.9%), compared with the rural students (15.6%), the situation of overweight/obesity of the urban students (23.8%) was more serious, the prevalences of overweight/obesity were separately 22.6%, 19.2% and 17.5% among developed, middle-developed and undeveloped social economic status subgroups. The boys with physical activities no more than 1 hour per day were more likely to be overweight/obese, with the OR of 1.09 (95%CI: 1.02, 1.17). The girls with screen time more than 1 hour per day or homework time more than 2 hours per day were more likely to be overweight/obese, with the ORs of 1.13 (95%CI: 1.02, 1.26) and 1.18 (95%CI: 1.03, 1.35) respectively. The high level of sedentary behaviors (more than 135min per day) was associated with overweight/obese in the girls, and the OR was 1.19 (95%CI: 1.08, 1.33). There was no significant heterogeneity of effect values between physical activities and overweight/obesity in the boys and between sedentary behaviors and overweight/obesity in the girls across the different provinces (P> 0.05). Conclusion: The associations among physical activities, sedentary behaviors and overweight/obesity existed in Chinese children aged 9-11 years, which were different in boys and girls. There was no statistically significant heterogeneity across different provinces. The strategies to prevent and control overweight/obesity in primary school students should focus on genderspecific needs.