The UDP communication function between the reader’s upper and lower computer of the surface acoustic wave radio frequency identification system is realized by using the ARM and the UDP protocol. Compared with the serial communication, the data transfer rates of UDP communication can be up to 100 Mbit/s, which makes full use of Ethernet resource for data transfer. Based on the UDP communication, the system supports the hot plug of the Ethernet cable. The human-machine interface of the reader upper computer is designed by the C# software, which can display the tag echo signal and decode the tag. Also the lower computer can be controlled by the interface, by which the human-computer interaction function is realized.