The invention relates to a railway-vehicle air-conditioner air supplying and returning system, which comprises air conditioners, wherein the air conditioners are arranged at both ends of a vehicle top, a through-type main air channel is arranged above a guest-room flat-top plate, an air outlet of each air conditioner is connected with the main air channel, and air is supplied to a guest room by the main air channel through an air-supplying opening which is formed below the main air channel; each air conditioner is provided with a first air-returning opening which is fixed to a vehicle-end flat-top plate and a second air-returning opening which is positioned above the vehicle-end flat-top plate, the lower edge of a guest-room lateral top plate is fixed to a connecting iron which is arranged on a lateral-wall framework through bolts, a cushion block is arranged between the connecting iron and the upper surface of the lower edge of the lateral top plate, an air-returning channel is formed between the lateral top plate and a lateral wall, and the air-returning channel is communicated with the second air-returning opening. According to the railway-vehicle air-conditioner air supplying and returning system, two air-returning channels are respectively formed between the guest-room lateral top plate and the two lateral walls, and the air-returning openings are formed in a vehicle-end flat top. One part of circulating air in a vehicle enters the upper space of a vehicle top through the air-returning channels and flows back to a machine set, and the other part of the circulating air directly flows back to the machine set through the air-returning openings in the vehicle-end flat top. According to the scheme, the airflow organization in the vehicle is improved, and the uniformity of a temperature and humidity field and a velocity field is improved.