Objective: To investigate the influencing factors of smoking tendency of adolescents and to analyze the influence of e-cigarette on smoking tendency of teenagers and the possible interaction, to provide evidence for tobacco control measures. Methods: Stratified multistage cluster probability sampling method was used to select 6 178 students from junior middle school, high school and vocational high school students in Shanghai for questionnaire survey from September to October 2019. Students with smoking tendency were taken as case group, adolescents with same sex and similar age(within 1 year) were mathed in 1∶3 ratio. A total of 631 adolescents with smoking tendency and 1 870 non-smoking tendency were included in the study. Conditional Logistic regression was used to analyze the influencing factors and possible interactions. Results: After adjusting gender, age and other covariates, conditional Logistic analysis results showed that the smoking tendency of middle school students was associated with factors such as their friends smoking, trying cigarettes and trying e-cigarettes. The OR value and 95%CI were 3.26(2.47-4.29), 5.90(3.76-9.24), and 3.28(2.11-5.10), respectively. The interaction analysis results showed that the OR value and 95%CI of the multiplying interaction between friends smoking and trying e-cigarettes, trying smoking and trying e-cigarettes were 8.62(4.90-15.17) and 12.01(6.02-23.95), respectively. There was no additive interaction. Conclusion Tobacco control interventions, such as e-cigarette harm publicity and peer education, can help to change teenagers smoking tendency and further reduce their tobacco use rate.