Objective To explore the mediating effect of sleep duration on the relationship between qi stagnation constitution and anxiety/depression in junior high school students.Methods From March 20 to March 31,2020,a total of 10,325 students from 6 junior high schools in Henan,Liaoning,Shaanxi,Shandong,and Fujian provinces were sampled by cluster sampling.Firstly,the general conditions(age,gender,grade,hometown,whether they are an only child)and sleep duration were collected,and their qi stagnation constitution,depression and anxiety status were evaluated by using the Qi Stagnation Subscale in the"TCM Constitution Classification and Judgment Scale",the Patient Health Questionnaire(PHQ-9)and the Generalized Anxiety Disorder(GAD-7).Secondly,Spearman correlation analysis was used to explore the correlation between qi stagnation constitution,sleep duration,and anxiety/depression.Then,linear regression analysis and mediating effect test were used to explore the relationship between qi stagnation constitution and anxiety/depression in junior high school students,and the mediating effect of sleep duration was analyzed,and the results were verified.Results(ⅰ)The detection rate of anxiety in non-only children was higher than that of only children(x2=11.198,P=0.001);The detection rate of anxiety(x2=106.967,P＜0.001)or depression(x2=84.692,P＜0.001)was higher among senior students than those in lower grades,while those of girls with anxiety(x2=100.441,P＜0.001)or depression(x2=71.418,P＜0.001)were higher than those of boys.The detection rates of anxiety(x2=1 092.298,P＜0.001)and depression(x2=866.740,P＜0.001)in qi stagnation constitution students were higher than those of non-qi stagnation constitution students,and the detection rates of anxiety(x2=1 076.716,P＜0.001)and depression(x2=1 099.725,P＜0.001)in students whose sleep duration less than 8 h were higher than those of whose sleep duration more than 8 h,and the shorter the sleep duration,the higher the detection rate.(ⅱ)Qi stagnation constitution positively predicted anxiety/depression(β=0.679,P＜0.001;β=0.718,P＜0.001),and sleep duration had a negative predictive effect on anxiety/depression(β=-0.403,P＜0.001;β=-0.439,P＜0.001).(ⅲ)Sleep duration played a partial mediating role in the relationship between qi stagnation constitution and anxiety/depression in junior high school students,and the mediating effect accounted for 13.40％and 13.79％of the total effect,respectively.Conclusion Although qi stagnation constitution mainly affects anxiety/depression through direct effect,it can still be partially indirectly realized through the mediating variable of sleep duration,that is,the shorter the sleep duration,the higher the risk of anxiety/depression in junior high school students.Therefore,the mental health problems of junior high school students can be prevented and improved by regulating qi stagnation constitution and ensuring adequate sleep duration.