Abstract: Objective Extreme passenger flow conditions characterized by sudden changes in passenger load may occur at interchange stations for urban rail transit trains. During such conditions, if the air supply system fails to provide sufficient air within the station dwell time, the air spring suspension system may be unable to lift the carbody off the emergency rubber stacks upon train start-up. This can adversely affect ride comfort and braking safety. Therefore, it is necessary to study the air supply system performance in urban rail transit trains under extreme passenger boarding/alighting conditions. Method A model of the train air supply system and air spring suspension system is established. The performance of the air supply system under different air reservoir configurations is simulated for the extreme boarding condition of completing AW0（empty load） to AW3（overload） process within station dwell time, and for the extreme interchange condition of AW3-AW0-AW3 process. Result ＆ Conclusion Configuring air spring reservoirs has significant effect on the air spring suspension system, enabling it rapidly restore air spring pressure to the specified level during load changes under extreme mass passenger flow boarding/alighting conditions. The volume of the air reservoir should be determined based on multiple factors, including the volume of the air springs and additional reservoirs, station dwell time, actual passenger volume, and available installation space on the vehicle. This method can be used for parameter optimization of train air supply systems to ensure performance requirements are met under extreme operating conditions.