Control method and device for draught fan of outdoor unit of air conditioner and air conditioner

The invention discloses a control method for a draught fan of an outdoor unit of an air conditioner. The method comprises the steps that after the draught fan is controlled to operate through response to a starting instruction, a system load of the air conditioner is obtained at random time intervals or preset time intervals, and operation of the draught fan is controlled on the basis of the system load of the air conditioner; when the system load of the air conditioner is smaller than a preset system load range, the rotational speed of the draught fan is lowered; when the system load of the air conditioner is larger than the preset system load range, the rotational speed of the draught fan is increased. By the adoption of the control method for the draught fan of the outdoor unit of the air conditioner, it is guaranteed that the draught fan operates at a high rotational speed when the air conditioner operates at a high load, and the draught fan operates at a low rotational speed when the air conditioner operates at a low load, so the stable operation of an air conditioning system is ensured, the rotational speed of the draught fan can also be lowered when the air conditioner load is low, and consequently noise and power consumption of the draught fan can be reduced. The invention further discloses a corresponding control device for the draught fan of the outdoor unit of the air conditioner and the air conditioner.