A fan system includes a connecting device, a controlling device and a fan device. The connecting device includes a first pin receiving at least one driving signal, and a second pin receiving a start signal, wherein a length of the first pin is greater than a length of the second pin. The controlling device is electrically connected with the connecting device and includes an enabling unit. The enabling unit generates at least one first enabling signal according to the start signal, and the controlling device outputs the driving signal and the first enabling signal. The fan device is electrically connected with the controlling device and includes at least one fan. The fan device transmits the driving signal to the fan and drives the fan according to the first enabling signal.