The implantable medical device is for implantation into a patient's body and is wirelessly powered by an external control device. The implantable medical device is induced by an AC electromagnetic field of the external control device through an inductive coil. A rectifier converts the AC electromagnetic field into a DC current. A detector detects a voltage value of the DC current, and a processor produces a first piece of status information accordingly. A transceiver receives and relays the first piece of status information to the external control device so as to monitor the power consumption of the implantable medical device when it is wirelessly powered.