Objective: To describe the current situation of leisure time physical activity, sedentary behavior, and sleep duration of children and adolescents aged 6-14 in Beijing, and provide a reference basis for guiding school age children to carry out reasonable physical activities and formulating effective intervention measures. Methods: A multistage stratified cluster random sampling method was used to investigate the nutritional and health status of 3 460 students in the first,third,fifth and seventh grades. Through the questionnaire surveys, the basic information of children and families and the activity information of children physical activity, sedentary behavior, and sleep were collected and statistically analyzed. Results: The results showed that the median time of children daily leisure time physical activity (LTPA) was 20.0 (8.6, 38.6) min, children in suburb areas (18.6 min) and seventh grade (14.3 min) had shorter LTPA time( Z/H =5.12，119.11， P <0.01). The average daily sleep duration of children was (8.71 ± 0.76) h, the proportion of school age children with insufficient sleep reached 54.7%. With an increase in grades, the incidence of insufficient sleep increased significantly ( χ 2=407.13， P <0.01). The median daily sedentary time of children was 195.7(145.0, 255.7 ) min, and 84.5% of children engaged in more than two hours of sedentary behavior every day. Urban (202.9 min) and obese children (210.4 min) had longer sedentary behavior time, and with the increase in grade, the daily sedentary behavior time of children gradually increased ( Z/H =5.04，14.83，637.98， P <0.01). Conclusion Children and adolescents aged 6-14 years in Beijing have less LTPA time, too much sedentary time, and insufficient sleep duration. Grade is an important factor affecting physical activity, sedentary behavior, and sleep duration of children, and body shape may be related to their sedentary behavior and sleep time.It is suggested that targeted policies should be adopted for children of different grades to increase their physical activity and reduce their sedentary behavior to promote their healthy development.