目的 对上海市初中生尝试吸烟的环境感知系统进行分析，为初中生控烟工作提供依据。方法 通过横断面研究，采用分层整群抽样的方式，对上海市23所初中的12 413名初中生的尝试吸烟情况及环境感知系统进行调查；并对感知系统中的因素进行Logistic回归分析，分析其对尝试吸烟的影响。结果 初中生尝试吸烟率为6.8%，男生的尝试吸烟率为9.3%，明显高于女生的4.6%（P<0.001）。多因素Logistic回归分析结果显示：环境感知系统中的7项因素对初中生尝试吸烟行为均有影响，主要因素包括同伴吸烟压力（OR=4.12，95%CI：3.50～4.84)、家庭烟草暴露多（OR=1.46，95%CI:1.38～1.96）、媒体烟草暴露多 (OR=1.40，95%CI:1.19～1.65) 以及吸烟认同度高 (OR=1.37，95%CI:1.17～1.60)。结论 环境感知系统中各项因素均与初中生尝试吸烟行为的发生密切相关，应作为初中生控烟工作的重点。

Objective To analyse the perceived environment system of tobacco experimentation among junior middle school students in Shanghai. Methods Cross-sectional study was conducted among 12 413 students from 23 junior middle schools in Shanghai by stratified cluster sampling. The conditions of tobacco experimentation and perceived environment system of these students were surveyed. The potential factors in perceived environment system were assessed using Logistic regression analysis, and their impact on tobacco experimentation was analysed. Results The rate of tobacco experimentation in junior middle school students was 6.8%. The rate of tobacco experimentation of boy students was 9.3%, which was significantly higher than that of girl students (4.6%)(P<0.001). Multivariate regression analysis indicated that 7 factors in perceived environment system had impact on tobacco experimentation in junior middle school students, which included high smoking press from peers (OR=4.12, 95%CI: 3.50-4.84), more exposure to cigarette smoke in family (OR=1.46, 95%CI: 1.38-1.96), more exposure to smoking from media (OR=1.40, 95%CI:1.19-1.65) and high tobacco use acceptance (OR=1.37, 95%CI:1.17-1.60). Conclusion Factors in perceived environment system are closely related to tobacco experimentation in junior middle school students, which should be attached great importance in tobacco control among junior middle school students.