Objective: To explore the association between sleep quality and cardiorespiratory fitness among secondary school students, so as to provide a reference for promoting the overall development of physical and mental health of Chinese adolescents. Methods: From September to December 2023, 5 713 secondary school students aged 13 to 18 years were selected by the stratified cluster random sampling method from Shanghai, Suzhou, Taiyuan, Wuyuan, Xingyi, and Urumqi, respectively. Sleep quality and cardiorespiratory fitness level of secondary school students were evaluated by Pittsburgh Sleep Quality Index(PSQI) combined with cardiorespiratory fitness test, and the association between sleep quality and cardiorespiratory fitness was analyzed by Pearson s correlation and multivariate linear regression. Results: The report rate of poor sleep quality among secondary school students was 33.7 %(1 926/5 713). The PSQI scores of girls aged 13-18 years were higher than those of boys ( χ 2=1.60, 12.78, 15.62, 3.04, 10.09, 13.65 ) ( P <0.05). The 20 m SRT of secondary school students was 40 (27，51) times, and the VO 2max was 46.27 (40. 84 ，51.30) mL/(kg min). The 20 m SRT and VO 2max of girls of all ages were lower than those of boys( Z =-15.27 to -6.41 , -18.06 to -14.07, P <0.05). Cardiorespiratory fitness (VO 2max) was negatively correlated with sleep duration and hypnotic medication scores in boys ( r =-0.032, -0.005); VO 2max was negatively correlated with sleep duration and daytime dysfunction scores in girls ( r =-0.028, -0.008) ( P <0.05). After controlling the related variables, linear regression analysis showed that the total PSQI score was negatively correlated with VO 2max among secondary school students( β =-0.347, P <0.01). Conclusions Secondary school students with better sleep quality have higher levels of cardiorespiratory fitness. Sleep quality should be promoted to improve cardiorespiratory fitness levels in secondary school students.