近年来，青少年焦虑、抑郁的发病率逐年上升，而作为青少年心理健康的重要组成部分，青少年焦虑、抑郁的影响机制值得探究。在本研究中将对抑郁和焦虑同时进行探究，研究青少年焦虑、抑郁的影响机制，为青少年心理健康的研究提供实证支撑。此外，在以往研究的基础上，本研究立足于青少年体育锻炼，探究同伴关系在青少年体育锻炼和青少年焦虑、抑郁之间所起的作用。

本文以身体锻炼等级量表(PARS-3)，同伴关系量表，青少年抑郁和焦虑量表，通过普查的方式，针对某一初中学校共收集到1503份有效数据。以方差分析、非参数检验、结构方程模型和随机森林为主要方法，通过进一步的研究，得出以下结论：（1）通过方差分析和非参数检验的方式，得到性别、年级、家庭教养方式、家庭权力结构等因素对青少年焦虑、抑郁均有着显著的影响；年级、家庭权力结构、家庭教养方式均显著影响青少年同伴关系。（2）通过结构方程模型对数据进行分析，得知同伴关系在体育锻炼对焦虑和抑郁的影响中均起部分中介作用，同伴关系在体育锻炼对焦虑的影响中间接效应占总效应的比例为37%；同伴关系在体育锻炼对抑郁的影响中间接效应占总效应的比例为40%。（3）为了进一步判断在不同类别下同伴关系的中介效应，采用随机森林的方法，得到班级排名是青少年抑郁和焦虑的重要影响因素，并且不同班级排名下同伴关系在体育锻炼对青少年焦虑和抑郁的影响中发挥不同的作用。

In recent years, the incidence of adolescent anxiety and depression has increased year by year, and as an important part of adolescent mental health, the influence mechanism of adolescent anxiety and depression is worth exploring. In this study, depression and anxiety will be explored at the same time, and the influence mechanism of adolescent anxiety and depression will be studied, so as to provide empirical support for the research on adolescent mental health. In addition, based on previous studies, this study explores the role of peer relationship between adolescent physical exercise and adolescent anxiety and depression based on adolescent physical exercise.

In this paper, a total of 1503 valid data were collected for a junior high school by means of a physical activity scale (PARS-3), peer relationship scale, and adolescent depression and anxiety scale. Taking ANOVA, nonparametric test, structural equation model and random forest as the main methods, through further research, the following conclusions are reached: (1) through ANOVA and nonparametric test, it is obtained that gender, grade, family parenting style, family power structure and other factors have a significant impact on adolescent anxiety and depression; Grade, family power structure, and family parenting style all significantly affect adolescent peer relationships. (2) The data were analyzed through the structural equation model, and it was found that peer relationship played a partial mediating role in the effects of physical exercise on anxiety and depression, and the indirect effect of peer relationship in the effect of physical exercise on anxiety accounted for 37% of the total effect; Peer relationships accounted for 40% of the indirect effects of physical activity on depression. (3) In order to further judge the mediating effect of peer relationship under different categories, the random forest method was used to obtain class ranking as an important influencing factor of adolescent depression and anxiety, and peer relationship under different class rankings played different roles in the effect of physical exercise on adolescent anxiety and depression.