Objective: To improve physical activity by assessing pedometer-based physical activity during specific intervals over a week, among junior high school students,and to provide a reference for improving the level of students’ physical activity. Methods: Students (n=675) of grades 6-8 from six public junior high schools in Shanghai were recruited and instructed to wear a pedometer for a week, step counts and contents were recorded over a specific period. This period mainly included steps taken on the way to and from school, at school, at home in the evening on weekdays, and in the morning, afternoon, and evening on weekends. Results: The daily step counts recorded were 8 332 steps, with those on weekdays showing significantly higher values than step counts on weekends (9 065 steps vs. 6 392 steps)(t=22.9, P<0.01). Proportionately, the physical activity level at school contributed more to daily step counts (61.3%), followed by those on the commute to and from school(25.5%). Boys were more active than girls. For all intervals on weekdays, the step counts of students in rural districts, with overweight or obese, in grades 6 and 7, were higher than those in urban districts, with normal status, in grade 8 respectively (P<0.05). Low-activity students with physical education were more active than one without physical education(t boy=1.99,t girl=2.45,P<0.05). Conclusion These findings facilitate the implementation of effective, feasible interventions to enhance physical activity over a series of intervals during the day.