The invention provides an adaptive frequency modulation energy-saving method for a multi-core multi-thread intrusion detection device, and is mainly applicable to network equipment (or a computer system) for supporting frequency conversion during operation. The method includes following steps: 1) predicting the flow change condition in a future period according to the current flow condition; 2) enumerating all possible frequency operation sequences in the future period, and obtaining state data of the current processor, such as equipment operation frequency, the length of a buffer area of the current network data packet, and the occupied condition of the buffer area of the current network data packet; 3) sending the state data of the processor, the flow change condition in the future period, and the frequency operation sequences to an internal model, performing simulation of each frequency operation sequence by the internal model, and selecting the optimal frequency operation frequency; and 4) applying the optimal frequency operation sequence to a real processor.