A fan system, which is driven by any of an AC power source and a DC power source, includes a fan motor, a voltage stabilizing module and a driving circuit connecting to the fan motor. The voltage stabilizing module includes an input end and a voltage conversion unit. The input end is coupled to an AC power source or a DC power source, and the voltage conversion unit is coupled to the input end for receiving the inputted DC or AC power. The voltage conversion unit keeps the DC or AC power at a working voltage level, which acts as a voltage signal to be transmitted to the driving circuit. The driving circuit receives the voltage signal and drives the fan motor to rotate accordingly.