Objective: To analyze the association between sleep duration and social anxiety in Chinese children and adolescents to provide evidence for promoting healthy lifestyle and mental health in children and adolescents. Methods: A total of 1 145 children and adolescents aged 7-16 were recruited by cluster random sampling in Beijing in 2020, and received a series of body measurements and questionnaire survey. Social Anxiety Scale for Children (SASC) and Pittsburgh Sleep Quality Index (PSQI) were used to evaluate the social anxiety symptoms and sleep duration of children and adolescents. T test was used to compare the differences of social anxiety level in different groups, and multivariate linear regression analysis was used to analyze the relationship between sleep duration and social anxiety. Results: The average score of social anxiety was (5.47±4.18). The social anxiety score of girls, participants aged 13-16, with insufficient physical activity and insufficient sleep duration were higher ( t =-4.34, -6.14, 3.35, 2.93, P < 0.05). The results of multivariate linear regression model showed that after adjusting confounding factors, social anxiety decreased by 0.78 for each additional hour of sleep duration ( β =-0.78, 95% CI =-1.03--0.54, P <0.01), with 0.60 in boys (95% CI = -0.95 --0.25), 0.90 in girls (95% CI =-1.24--0.56), 0.75 among participants aged 7-12 (95% CI =-1.11--0.40) and 0.76 among participants aged 13~16 (95% CI =-1.11--0.41)( P <0.01), respectively. Social anxiety among participants who were not over weight or obese decreased by 0.78(95% CI =-1.09--0.48) and 0.81 among overweight and obese group (95% CI =-1.22- -0.41 )( P <0.01) for each additional hour of sleep duration, respectively. Conclusion Substantial differences in social anxiety are observed in children and adolescents by gender, age group and nutritional status. Sufficient sleep duration is significantly related to the decrease of social anxiety, and improve the overall level of student mental health.