The cross-flow fan is mainly composed of impeller, air duct and motor. It uses a relatively long cylindrical impeller to work, the gas enters from one side of the outer edge of the impeller, and then passes through the inside of the impeller to discharge from the other side, the gas is affected by the blade force twice in the impeller, so the wind pressure is high, the air flow can reach a higher distance. Its outlet section is narrow and long, and the axial length can be arbitrarily selected without affecting the flow state of the gas.