The invention relates to a method for controlling a dust removal device of a heat exchanger of an outdoor machine of an air conditioner. The dust removal device comprises a fan and control equipment, wherein the control equipment comprises a timer, a receiver, a judger and an actuator; and the control equipment controls the fan to reversely rotate for dust removal. The method is characterized by comprising the following steps that: when the air conditioner normally operates, the receiver continuously receives operating parameter information which is fed back by the air conditioner and transmits the operating parameter information to the judger; the judger judges the operating parameter information; when the judger determines that the operating parameter information meets a preset dust removal mode operating condition, the air conditioner operates for dust removal; the actuator controls a compressor of the air conditioner to stop operating; the timer clears the accumulated operating time of the air conditioner and the continuous operating time of the compressor; the actuator controls the fan to stop, the timer starts timing, and when time is equal to first time T1, the judger determines that the fan is in a static state; the actuator controls the fan to start and rotate in the opposite direction relative to the normal operation direction; the timer re-starts timing, and when the time is equal to second time T2, the actuator controls the fan to stop; the timer re-starts timing, and when the time is equal to third time T3, the judger determines that the fan is in the static state; and the air conditioner quits a dust removal mode, starts to normally operate or is directly powered off. By the method, the normal operation of the air conditioner is not influenced, the air conditioner can automatically remove dust, and the service life of the air conditioner can be prolonged.