Rail transit, as an important public transport facility in the city, is highly crowded, which easily leads to the spread of pathogenic microorganisms such as viruses. The air conditioning unit of the train adopts the refrigeration mode that the fresh air in the tunnel and the return air in the passenger room is filtered by the filter screen and then sent to the passenger room. The cleanliness of the carriage ventilation system is related to the air quality in the train and the comfort of passengers. It is also the "dead corner" of pathogenic microorganism hiding. The installation of "UV automatic timing sterilization and disinfection device" on air conditioning units of rail transit vehicles can not only save the cost of human disinfection, but also help to ensure the air quality in the train and reduce the risk of virus transmission.