A fan control method, apparatus, and system, so as to implement speed regulation and rotation direction control on a four-wire system counter-rotating fan with a conventional four-wire fan interface by using a PWM control bus. The method provided by the embodiments of the present invention includes: receiving a first fan regulation and control signal sent by a system control module; converting the first fan regulation and control signal to a forward-rotating control signal, a counter-rotating control signal, or a rotation direction switchover control signal according to a duty cycle range of the first fan regulation and control signal and a current rotation direction of the fan; and sending a control signal obtained by the conversion to a fan driving module, so that the fan driving module drives, according to the control signal obtained by the conversion, the fan to operate.