Objective: To investigate the prevalence of adolescents dietary behavior in Shanghai, and to explore emotional influence on dietary behavior. Methods: A total of 7 456 students from 10 junior and 6 senior high schools in Shanghai were selected to participate in the questionnaire survey with the stratified random cluster sampling method. The survey included general information, eating behavior, PHQ-2 and GAD-7. Results: During the past week, the proportion of adolescents in Shanghai reported consumption of sugar sweetened beverages, sweet desserts, frequent fried food and fast food (≥4 times/week) were 13.26%, 16.90%, 6.99 % and 13.01%, respectively. The proportion of students reported consumption of fruits, vegetables, milk and breakfast every day were 56.96%, 73.00%, 65.03% and 76.11%, respectively. There were significant differences by sex and educational stages(both P <0.05). Adolescents with depression or anxiety have a higher incidence of unhealthy eating behaviors than those without depression or anxiety( P <0.01). After adjusting for gender, school, accommodation, grades, pocket money and social class, depression and anxiety increase the risk of various unhealthy eating behaviors in adolescents( P <0.05). Compared with those without anxiety, the risks of sugar sweetened beverages consumption (≥1 time/d) among adolescents with mild and moderate to severe anxiety were 1.42 times (95% CI =1.20-1.67) and 2.51 times (95% CI =2.09-3.01), the risks of insufficient fruits consumption (<1 time/d) were 1.30 times (95% CI =1.16-1.45) and 1.28 times (95% CI =1.11-1.47), the risks of insufficient vegetable consumption (<1 time/d) were 1.35 times (95% CI =1.20-1.52) and 1.41 times(95% CI =1.21-1.65), the risks of insufficient milk consumption (<1 time/d) were 1.29 times (95% CI =1.15-1.44) and 1.20 times(95% CI =1.04-1.39), and the risks of breakfast skipping were 1.75 times (95% CI =1.54-1.99) and 2.97 times (95% CI =2.55-3.46) among adolescents with mild and moderate to severe anxiety. Conclusion The proportion of unhealthy eating behaviors among adolescents in Shanghai is still high. Early education and intervention for students eating behaviors should be carried out, and attention should be paid to the occurrence of adolescents negative emotions, so as to reduce the risk of unhealthy eating behaviors among adolescents through the promotion of mental health.