Background <p>Adolescence is a critical period for physical and mental health development. Chinese adolescents face multiple challenges such as academic pressure, with considerable mental health risks. Positive health behaviors are closely associated with physical and mental health, but their complex interaction network remains unelucidated.</p> Methods <p>Cross-sectional survey was conducted on 436 middle school students with positive health behavior scale and SCL-90. The network of 15 nodes (10 mental health symptoms and 5 positive health behaviors) was constructed by network analysis. The stability of the network was tested by correlation stability analysis. The core nodes were determined by centrality index. The cross-system association strength was analyzed by bridge effect expectation (BEI).</p> Results <p>The network showed robust stability (CS coefficient = 0.75). Anxiety was the core node in mental health symptoms, positively correlated with somatization (<i>r</i> = 0.26) and hostility (<i>r</i> = 0.22). Circadian self-regulation was positively correlated with psychopathology (<i>r</i> = 0.52). Physical activity served as a cross-system bridge, negatively correlated with depression (<i>r</i> = -0.08). No significant gender differences in network characteristics were observed.</p> Conclusion <p>Adolescent positive health behaviors and mental health form a complex association network. Anxiety is a core driver of psychological symptoms, and physical activity is a key cross-system bridge for improving mental health. The findings provide a theoretical basis for developing targeted intervention strategies focusing on physical activity.</p>