Objective: To explore the association between physical activity and sleep quality among middle school students, so as to provide reference for adolescent sleep improvement. Methods: From September to December 2023, 5 713 middle school students aged 13-18 years were selected from Shanghai, Suzhou, Taiyuan, Wuyuan, Xingyi and Urumqi by stratified cluster random sampling method. Pittsburgh Sleep Quality Index (PSQI) and Evaluation of Physical Activity Levels of Children and Adolescents Aged 7-18 Years were used to investigate and evaluate sleep quality and physical activity. Comparisons between groups were made using the t-test, Mann-Whitney U-test, and associations between physical activity and sleep quality of middle school students were analyzed using Spearman correlation and linear regression methods. Results: The total PSQI scores were 4.0(2.0,6.0) and 5.0 (3.0,6.0) for boys and girls, respectively, with significant sex difference ( Z =-10.90, P <0.01); light physical activity(LPA) and moderate to vigorous physical activity(MVPA) of boys were 18.57 (2.86, 42.86) and 68.57 (35.71, 119.18)min, and girls were 14.29 (0.00, 30.00) and 55.71 (31.43, 92.86)min respectively, and the differences were statistically significant ( Z =3.65, -8.65 , P <0.01). The results of Spearman correlation regression showed that adolescents MVPA was negatively correlated with the total PSQI score ( r =-0.04, P <0.01). After controlling for variables such as mental health, nutritional status and maximum oxygen uptake, the results of linear regression analysis showed that PSQI total score negatively predicted MVPA among middle school students ( B =-4.76, 95% CI =-7.16 to -2.36, P <0.05). Conclusion The longer the duration of physical activity among middle school students, the better the quality of sleep.