Abstract: Objective To understand the status and relation of sedentary behavior with subjective well-being among children and adolescents, so as to provide a reference for promoting the mental and physical health of children and adolescents. Methods Data were collected from reports of 628 students in grade 4-8 from one public primary school and one public middle school in Shanghai, by self-evaluation questionnaires regarding TV watching, Internet addiction, game addiction, life satisfaction, personal well-being, positive and negative affect. Results The rate of subjects that were watching TV, doing homework, online and playing video games for a long time was 2.7%,6.0%, 3.6%, 5.1%, respectively. The incidence rate of excessive Internet use and excessive game use was 14.3% and 8.2%, respectively. Long-time Internet access, long-time video games, excessive Internet use and excessive game were negatively correlated with the scores of satisfaction with life scale, personal wellbeing index and positive affect. While negative affect score was positively correlated with those above(P<0.05). The linear-regression analysis showed that the frequency of online games had significant predictive effect on subjective well-being in most domains. Conclusion In order to promote the health of the children and adolescents, attention should be paid to the intervention of sedentary behavior, especially the excessive usage of online games.