The present invention relates to a method and a device for filtering a novel custom Ethernet out-band data packet. The key of the method and the device is that a filter module is additionally arranged between the out-band management interface of the Ethernet switcher and the CPU to extract the keyword of the data packet, to filter the content of the relative data packet, and to operate the discarding or the flow control operation. The method and the device can provide one to seven layers of filtering to the Ethernet out- band data packet, to pre filters the layer 2 or layer 3 or layer 4 data packets used to be processed by the CPU, and the present invention can pre process the special protocol data packets such as an Ethernet broadcast packet, a multicast packet, other Ethernet management protocols, the IP and a high-level IP protocol data packet, an ICMP and an ARP, etc., therefore, the processing efficiency of the CPU is improved, and the overload operation caused by the protocol data packets flooding is avoided, thereby the reliability of the complete Ethernet switcher system is improved.