A packet processing system for a network packet delivery device and a method thereof are provided. The packet processing system includes a packet receiving module for receiving packets transmitted from an external device; a packet replication module for replicating the packets received by the packet receiving module, wherein the number of packet replications is determined based on the number of members in the multicast group; a packet modification module for replacing each of destination addresses in frame headers of a media access control of each of the packets replicated by the packet replication module with an address information of each of the members in the multicast group; and a packet transmission module for transmitting the packets, according to the destination addresses, to a packet receiving terminal having an address corresponding to the destination addresses.