Abstract: The air quality in the urban railway carriages has a significant impact on travelling experience and health conditions because of relatively high passenger density. Taking the train carriage of urban rail transit as an example, the computational fluid dynamics（CFD）FLUENT2019 is used to numerically simulate the air quality in the urban railway compartment with normal passenger load. The temperature distribution, velocity distribution and pollutant concentration distribution are analyzed by supply air speed of 2 m/s, 2.5 m/s and 3 m/s and supply air Angle of 30°, 45° and 90°, respectively. It is proposed that under the background of normalized epidemic prevention, the ventilation mode to ensure the best air circulation rate of the carriage is upper supply and lower return, the air supply speed is 3m/s and the air supply Angle is vertical 90°.