Objective: To analyze the second hand smoke exposure and related factors of nonsmoking junior middle school students in Beijing, so as to provide a data support for formulating tobacco control measures. Methods: The multistage cluster random sampling method was used to select junior middle school students in Beijing. The valid data of 4 494, 4 915 and 3 792 nonsmoking middle school students were obtained from three waves of youth tobacco epidemic surveillance in 2013 (September to October), 2019 (August to November) and 2021 (September to December) wave, respectively. The information was collected by the national youth tobacco epidemic surveillance questionnaire. The complex sampling data analysis module of SPSS 21.0 was used to descriptive analysis and multivariate Logistic regression. Results: The proportions of secondhand smoke exposure of nonsmoking junior middle school students in the four types of places in the past 7 days in 2013, 2019 and 2021 in Beijing were 76.4%, 71.4% and 65.7%, respectively, with statistically significant differences (χ2=126.10, P<0.01). The proportions of that found someone smoking in the campus in the three waves of survey were 34.7%, 27.9% and 21.1% (χ2=209.78), the proportion of that found teachers smoking daily were 2.7%, 1.8% and 1.3% (χ2=22.14) (P<0.01), respectively. Multivariate Logistic regression analysis showed both parents smoking (OR=8.47, 95%CI=4.36-16.48), father smoking (OR=3.51, 95%CI=2.75-4.49), and friends smoking (OR=1.88, 95%CI=1.39-2.55) were the influencing factors of secondhand smoke exposure in four types of places of nonsmoking junior middle school students in 2013. Both parents smoking (OR=2.37, 95%CI=1.33-4.22), father smoking (OR=2.80, 95%CI=2.33-3.37), friends smoking (OR=2.24, 95%CI=1.71-2.92), and teaching the tobacco hazards in class (OR=0.77, 95%CI=0.64-0.93) were the influencing factors of secondhand smoke exposure in four types of places for nonsmoking middle school students in 2019. Both parents smoking (OR=3.93, 95%CI=2.29-6.75), fathers smoking (OR=3.30, 95%CI=2.72-3.99), and teaching the tobacco hazards in the class (OR=0.81, 95%CI=0.68-0.97) were the influential factor of secondhand smoke exposure in four types of places of nonsmoking junior middle school students in 2021 (P<0.05). Conclusions The secondhand smoke exposure of nonsmoking middle school students in Beijing has improved, but still is a high level. It is necessary to take corresponding measures to effectively protect nonsmoking junior middle school students from the harm of secondhand smoke.