An adaptor plug assembly includes an adaptor plug and a mobile device which has a receiving unit. The adaptor plug includes a housing having a first connection end from which two terminals extends, and a second connection end in which three receptacle holes are defined. The two terminals are connected to the second connection end. A coil is mounted to one of the two terminals and electrically connected to a micro controller which includes a calculating unit, a transforming unit and a wire-less transmitting unit. The transforming unit receives current inducted by the coil and transforms the current into a first signal which is sent to and calculated by the calculating unit to be a second signal which is transmitted by the wire-less transmitting unit to the receiving unit of the mobile device. A power unit is installed in the housing provides power to the micro controller.