Objective To investigate the prevalence and risk factors of depression among middle school students in Tianjin , and to provide the evidence for making targeted prevention of depression. Methods In September 2019 and September 2020, the stratified cluster sampling method was used to select 32 380 middle school students in Tianjin for face-to-face questionnaire survey, which included the basic information , depressive symptoms , health status , life and behavior habits , injuries , and Internet addiction in the previous week. The χ² test , t test, univariate and multivariate logistic stepwise regression were used to analyze the data. Results From 2019 to 2020, the prevalence of depression among middle school students in Tianjin was 20.48% , with higher prevalence in girls than in boys and higher prevalence in urban areas than in suburban areas. Multivariate regression results show that smoking, school bullying, parental abuse, Internet addiction , injury , urban area , female , sickness, anemia and sweets are risk factors for depression ; fruits , vegetables , breakfast , high Intensive exercise are protective factors. The OR ( 95%CI ) of depression of school bullying and parental beating and scolding were 4.71 ( 95%CI 3.84 -5.79) and 2.94 ( 95%CI 2.72 - 3.18); the OR ( 95%CI ) of depression of internet addiction students was 2.76 ( 95%CI 2.30 - 3.11); the OR ( 95%CI ) of depression in anemia students was 1.68 ( 95%CI 1.36 - 2.07); compared with non-smokers, the odd ratio(OR) ( 95%CI ) of depression for smoking less than 1 cigarette, 1-11 cigarette, and 11-20 cigarette per day were 1.83 ( 95%CI 0.75 - 2.44), 1.64 ( 95%CI 0.94 -2.84 ), 1.92 ( 95%CI 1.51 - 2.44), respectively; Conclusion The depression level of middle school students in Tianjin is in the middle, and the intervention should be interfered from many aspects, such as cultivating students' good living behavior habits and healthy body, providing good family atmosphere and campus environment.