Abstract: Objective To investigate physical activity and its determinants during leisure time among junior high school students in Jinshan District during the leisure time and to promote physical activity for children and adolescents. Methods Six primary schools were randomly cluster selected and then a class was selected from each grade, in which all students provided the informed consent record the content and time of static and dynamic physical activities on weekdays (from leaving school to arriving at school on the next morning) and on weekends (all day). Results The average of static activity time was 3.70 h and 7.85 h respectively during leisure time on weekdays and weekends; the students with higher grade spent more time on study-related activities and the students on the town also spent more time on static physical activity. The median of dynamic physical activities was 29.0 and 45.0 min respectively on weekdays and weekends, the median of MVPA (moderate and rigorous physical activity) was 14.0 and 17.5 min. About 36.0% students took the initiative transportation way on the weekdays and 11.4% students spent at least one hour on MVPA, the students of grade 7th, residence in town, academic performance above average preferred to MVPA. Conclusion Junior middle school students in Jinshan District have insufficient time for physical activity during the leisure time, and schools, families, and communities should make joint effort to promote physical activities.