A fan system includes a connecting device, a controlling device and a fan device. The connecting device has a plurality of pins receiving at least one driving signal and a start signal. The control device is electrically connected to the pins of the connecting device and has a start control unit. The start control unit generates a first enabling signal in accordance with the start signal. The control device synchronously outputs the first enabling signal and the driving signal. The fan device is electrically connected to the control device and has a plurality of fans. The fan device synchronously transmits the driving signal to the fans and synchronously drives the fans to rotate in accordance with the first enabling signal.