A system and method for reassembling packets in a packet relay node are provided. A packet relay node located between a transmitting node (i.e., a source node) and a receiving node (i.e., a destination node) inspects received packets to see if they are fragmented packets and reassembles a series of packets decided to be fragmented packets into an original packet, thereby reducing overhead and radio resource waste caused by duplicate transmission of IP headers having the same fragmented-packet information.