A wash-free air-guiding cover includes a cover having a body with a fixing seat disposed on a side thereof. A ventilation tube is disposed on the fixing seat and includes a ventilation hole intercommunicated with the other side of the body. An air guiding device is mounted to the fixing seat and includes a tube having first, second, and third air guiding spaces. The air guiding device further includes first and second sealing members and first and second flow guiding rods. Air flowing into the tube must flow zigzag through the first, second, and third air guiding spaces and between the first and second flow guiding rods and the second and third air guiding spaces, assuring smooth flow of air during the painting operation and avoiding the paint from leaking via the ventilation tube and the ventilation hole of the cover.