The present invention provides an auto-detection control apparatus, which receives an electric power from one of a system power source signal and an external device and performs a detection when coupled to the external device. The apparatus comprises a detection module, a power management module and a control module. The detection module generates a first result based on whether a first power signal from the external device exists, wherein the first result is related to whether the external device provides an electricity to itself. The power management module prevents a conflict between the system power source signal and the first power signal. The control module determines whether the electric power is supplied to the external device by the power management module based on the first result.