Objective：To investigate the knowledge，attitudes，and practices（KAP）of college students in Nanjing regarding fine particulate matter（PM_2.5）pollution and its impact on respiratory health，providing theoretical and practical guidance for respiratory health education. Methods：From August to November 2024，550 college students in Nanjing were recruited as study participants. An online questionnaire survey was conducted to assess KAP related to PM_2.5 pollution and respiratory health. Results：Among 451 valid responses，the accuracy rates of PM_2.5 related knowledge and respiratory health knowledge were only 43.53% and 40.30%，respectively. The mean attitude score was 3.38（out of a total of 4），while the mean behavior score was 3.00（out of a total of 4）. Multiple linear regression analysis revealed that economic status（monthly expenditure，household income）positively influenced knowledge（β=0.162， P ＜ 0.01）and behavior scores（β=0.283，P ＜ 0.01），whereas family history of respiratory diseases negatively affected knowledge scores （β=-0.108，P ＜ 0.05）. The structural equation model（SEM）confirmed the significant causal transmission effect of knowledge，attitude [standardized path coefficients（SPC）=0.270，P ＜ 0.01]，and behavior（SPC=0.148，P ＜ 0.01）. A total of 42 significant influence pathways were identified，though some knowledge components including respiratory protection exhibited negative associations with behavior，suggesting that contextual factors such as life stress and time constraints may hinder behavioral adoption. Conclusion：The awareness and countermeasures of PM_2.5 pollution and its impact on respiratory health among college students in Nanjing City are generally weak. Respiratory health education based on factors such as university students’professional background，family income and age，targeted popularization of PM_2.5 prevention and control knowledge and should be carried out，and the effective transformation of college students’knowledge，attitude，and behavior should be promoted through multi-subject collaborative intervention.