Abstract: During metro train operation, the pollutants generated in the running tunnels will be emitted into the at? mosphere through ventilation pavilions. To understand the concentration distribution, composition, and morphological characteristics of particulate matters in metro running tunnels, a study was conducted based on four typical metro stations in Chengdu, Sichuan Province. The laser dust detector was used for on-site testing of particulate matter concentrations at the piston wind pavilions of the four stations. Particulate matter samples were collected for scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis to determine their sources. Pearson correlation coefficients were used to analyze the relationship between the running tunnel and ambient environmental conditions. The results show that the particulate matters generated by the train passing through metro running tunnels are mostly spherical or angular and so on, with elemental contents mainly consisting of metals such as Fe, Al, Ba, and Zn. These particles primarily originate from mechanical wear and friction at the interfaces between tracks and wheels, brakes, and the contact points between the pantograph and catenary during metro train operation. The concentration of PM10 is much higher than that of PM1 and PM2.5, with no significant correlation between the concentrations of particulate matters with different particle sizes. The particulate matter concentration in metro running tunnels is significantly influenced by the season, with PM2.5 and PM10 levels higher in winter than in other seasons,and PM10 emissions exceeding the standard limits. The Pearson correlation coefficients r for PM indicators at the four stations are all greater than 0.8, indicating a high linear correlation between the pollutant concentrations at the ventilation pavilions and the air pollution levels in surrounding environment.