The invention discloses an air-conditioner air supply speed control device and method and an air conditioner. The method includes the following steps: detecting distance between a user and the air conditioner through a distance measuring module by the air conditioner; automatically adjusting air supply speed according to the distance by the air conditioner. The air-conditioner air supply speed control device is arranged on the air conditioner; the air supply speed control method is used in a manner of being matched with the device, the distance between the user and the air conditioner can be measured through the distance measuring module, and automatic air supply speed adjusting can be realized according to the distance; when the user is close to an air outlet, air speed is lowered, and the user can feel gentle; when the user is away from the air outlet, the air speed is increased, and the user can feel cool or warm when being afar, so that resources are saved effectively, the air conditioner is utilized efficiently, the user can feel comfortable, and user experience is better.