Objective: To understand secular trend of sedentary behaviors of school-aged children and adolescents in leisure time in China, and to provide theoretical basis for health behavior intervention. Methods: Data from China Health and Nutrition Survey (CHNS) during 2006 to 2015 were used to analyze leisure sedentary behaviors of children and adolescents aged 6-17 years. Means and medians were used for basic description and trend analysis, and nonparametric test was used for statistical comparison. Results: The total time of sedentary behavior during leisure time among children and adolescents aged 6-17 years showed a significant increasing trend, in which computer time contributed the most, especially among 6-11-year-old group with a five-fold increase. The time spent watching TV and doing homework slightly decreased. There was no sex difference in the total sedentary time during leisure time(Z=1.74，1.54，0.08，1.50，P>0.05), but there was sex difference in time spent in computer and homework(Z=2.00，2.01，2.84，2.92，P>0.05). Total sedentary time, as well as sedentary time spent in watching TV, computer, and homework differed by age and areas(Z=52.49-75.21，54.21-136.31，24.58-44.55; 6.25-8.61，6.42-13.34，3.89-6.42，P<0.01). Conclusion Over the last decade, sedentary behavior increased during leisure time among Chinese children and adolescents, and the usage pattern has also changed substantially. Results suggest that relevant departments should adopt more strategies to reduce sedentary behaviors and strengthen physical activities.