The effect of PM2.5 exposure on lung function reduction has been well-documented, but the underlying mech-anism remains unclear. MiR-4301 may be involved in regulating pathways related to lung injury/repairment, and this study aimed to explore the potential role of miR-4301 in PM2.5 exposure-associated lung function reduction. A total of 167 Wuhan community nonsmokers were included in this study. Lung function was measured and personal PM2.5 exposure moving averages were evaluated for each participant. Plasma miRNA was determined by real-time polymerase chain reaction. A generalized linear model was conducted to assess the relationships among personal PM2.5 moving average concentrations, lung function, and plasma miRNA. The mediation effect of miRNA on the association of personal PM2.5 exposure with lung function reduction was estimated. Finally, we performed pathway enrichment analysis to predict the underlying pathways of miRNA in lung function reduction from PM2.5 exposure. We found that each 10 mu g/m3 increase in the 7-day personal PM2.5 moving average concentration (Lag0-7) was related to a 46.71 mL, 1.15%, 157.06 mL/s, and 188.13 mL/s re-ductions in FEV1, FEV1/FVC, PEF, and MMF, respectively. PM2.5 exposure was negatively associated with plasma miR-4301 expression levels in a dose-response manner. Additionally, each 1% increase in miR-4301 expression level was significantly associated with a 0.36 mL, 0.01%, 1.14 mL/s, and 1.28 mL/s increases in FEV1, FEV1/FVC, MMF, and PEF, respectively. Mediation analysis further revealed that decreased miR-4301 mediated 15.6% and 16.8% of PM2.5 exposure-associated reductions in FEV1/FVC and MMF, respectively. Pathway enrichment ana-lyses suggested that the wingless related-integration site (Wnt) signaling pathway might be one of the pathways regulated by miR-4301 in the reduction of lung function from PM2.5 exposure. In brief, personal PM2.5 exposure was negatively associated with plasma miR-4301 or lung function in a dose-response manner. Moreover, miR-4301 partially mediated the lung function reduction associated with PM2.5 exposure.