Athlete burnout significantly affects both athlete well-being and performance, potentially influenced by dietary patterns, sleep quality, screen time, and stress-coping strategies. However, the mechanistic interplay among these factors remains unclear. This study utilized a cross-sectional design to examine the relationships between daily health behaviors (including diet, sleep, and screen time), stress coping strategies, perceived psychological strain and athlete burnout among Chinese competitive swimmers. A comprehensive questionnaire was developed, encompassing demographic information, eating behavior (BEDA), sleeping behavior (ASSQ), screen time, stress coping strategies (CSCA), perceived psychological strain (APSQ), and athlete burnout (ABQ). This questionnaire was administered online and distributed to participating athletes through a snowball sampling method during the 2024 Shanghai Youth Swimming Competition to enhance the sample size. Data from 1,071 swimmers (477 females, 44.5%) revealed through Lasso regression analysis that perceived psychological strain emerged as the strongest predictor of athlete burnout (β = 5.07), followed by age (β = 2.19) and athlete level (β = 3.76). Sleep disturbances (ASSQ) demonstrated a weaker yet significant contribution to ABQ (β = 0.92). A temporal inflection point in age-related burnout trajectories was identified at 19 years. This study identified psychological strain (APSQ) as the strongest predictor of burnout (ABQ) among Chinese swimmers (β = 5.07), underscoring the critical need for strain-specific management in prevention strategies. The significant effects of advancing age (β = 2.19) and increased training load (β = 3.76) further revealed the developmental nature of burnout across career stages, necessitating age-targeted interventions. Although sleep disorders (ASSQ) had a weaker influence (β = 0.92), their significant role supports the integration of sleep quality enhancement into a holistic strain-sleep intervention framework. These findings provide a novel pathway for athlete mental health management through prioritized strain regulation, hierarchical age-specific interventions, and synergistic sleep-stress protocols.