Objective: To explore the association between nap duration with anxiety and depressive symptoms among junior high school students, in order to provide evidence for mental health interventions for adolescents. Methods: From May to June 2022, a combination of convenience sampling and cluster sampling was used to select 2 491 students from 2 junior high schools in Haizhu District, Guangzhou City for questionnaire survey and physical examination. The questionnaire collected nap duration, night time sleep duration, bedtime, physical activity, and sedentary behavior. Anxiety and depressive symptoms were assessed using Patient Health Questionnaire-9 (PHQ-9) and Generalized Anxiety Disorder-7 (GAD-7), respectively. Log-binomial regression model was used to analyze the association of nap duration with anxiety and depressive symptoms, as well as comorbidity among junior high school students, and a restricted cubic spline (RCS) Log-binomial regression model was employed to analyze the non linear relationship after adjusting for covariates. Results: The detection rates of anxiety symptoms, depressive symptoms and comorbidity among junior high school students were 13.29%,14.65%,9.19%. After adjusting for covariates such as age, gender and nighttime sleep duration, compared with a school day nap duration of <30 min/d, a nap duration of 30-<60 min/d was associated with a reduced risk of anxiety symptoms ( APR =0.68, 95% CI =0.49-0.98) and comorbidity ( APR =0.56, 95% CI =0.39-0.87)(both P < 0.05 ). Compared with no napping on weekends, a nap duration of 30-<60 min/d was associated with a reduced risk of anxiety symptoms ( APR =0.62, 95% CI =0.41-0.88), depressive symptoms ( APR =0.52, 95% CI =0.34-0.75) and comorbidity ( APR = 0.52 , 95% CI =0.30-0.83)(all P <0.05). RCS curves showed a nonlinear relationship between weekend nap duration and the prevalence of anxiety, depressive symptoms and comorbidity among junior high school students(all P non linear <0.05); weekend nap duration of <120 min was associated with a lower risk of anxiety and depressive symptoms, and weekend nap duration of >180 min was associated with an increased risk. Conclusions Appropriate nap duration can help reduce the risk of anxiety, depressive symptoms, and the comorbidity among junior high school students. Adolescents should be guided to reasonably arrange nap duration for promoting physical and mental health.