Abstract: The questionnaire survey, literature review, semi-structured interviews, and mathematical statistics were used to analyze the mental health of young people during the epidemic. Psychological symptoms, physical activity and intervention status and related influencing factors are analyzed. The results show that: Adolescents were in widespread anxiety; some of them had depression symptoms, and a few had post-traumatic stress disorder. Education level is an influencing factor in depression symptoms. Adolescents have low physical activity. Factors influencing physical activity include physical activity in 2019 and the length of online learning. During the epidemic period, the BMI index of adolescents is generally low but there are still a few high numbers. Diet and nutrition, and physical activities in 2019 have an impact on the BMI of adolescents. Adolescents' physical activity can prevent, alleviate psychological problems and promote mental health. Adolescents' mental health can also influence their participation in sports activities. The paper puts forward practical approaches: After the epidemic, we should promote the change of ideas and improve the mental health of adolescents; adjust the curriculum structure and cultivate the adolescents' habits of sports activities; build dynamic monitoring to promote young adolescents' physical and mental health.

Key words: the epidemic period, adolescents, physical and mental health, physical activity