A signal switching method applicable to a first electronic device includes: receiving a voltage of a second electronic device through a power supply contact pin of the first electronic device; comparing the voltage with a threshold; when the voltage is greater than the threshold, connecting a first bus of the first electronic device to at least one signal contact pin, and disconnecting a second bus of the first electronic device from the at least one signal contact pin; and when the voltage is not greater than the threshold, connecting the second bus to the at least one signal pin, and disconnecting the first bus from the at least one signal contact pin.