An implantable medical device includes a detecting unit, a control unit and a communication unit. The control unit uses a seizure prediction algorithm to predict epilepsy seizure events in real time based on physiological information detected by the detecting unit, and stores internal data which comprise the detected physiological information and prediction information about the prediction result. The control unit is configured to, in a first communication mode, control its memory unit and communication unit to transmit the internal data to the external monitoring device, and in a second communication mode, control the communication unit to receive an updated seizure prediction algorithm from the external monitoring device and stores the algorithm in the memory unit for predicting seizure events.