Objective: To examine mental health problems among adolescents in Taiyuan City and its relationship to chronotype, so as to give a scientific basis for supporting mental health of middle school students. Methods: From October to November 2021, a total of 2 621 pupils were enrolled from three junior high schools and two senior high schools in Taiyuan by using a multi stage stratified cluster random sampling method to investigate demographic characteristics, mental health status, and chronotype. Chi squared test, Spearman correlation analysis and Logistic regression were used to analyze the relationship between sleep patterns and mental health problems in middle school students. Results: The proportion of morning, intermediate and evening types of middle school students sleep were 17.9%, 65.6%, and 16.4%, respectively. The overall detection rate of mental health problems was 13.8 %, which was statistically significant among middle school students in different grades, self perceived family economic status, the number of friends and sleep patterns ( χ 2=42.69, 29.15, 46.02, 93.99, P <0.05). After adjusting for grade, self perceived family economic status and the number of friends, Logistic regression analysis revealed that mental health problems were positively associated with evening type ( OR =2.84) and negatively associated with morning type ( OR =0.61)( P ＜0.05). Conclusion Chronotype is associated with mental health problems among middle school students, with a higher risk for evening type and a lower risk for morning type. Mental health of middle school students can be enhanced by changing their chronotype.