Many coal enterprises have built the videoconference systems on their LAN (Local Area Network). As the development of these enterprises, their organizations are distributed over our country and even over the world. Therefore, the videoconference systems have to run over WAN (Wide Area Network). Normally, the structure of a videoconference system is center_division including MCU (multi control unit) and participants. No QoS and security assurance are available now because all videoconference system is based on TCP/IP. Therefore, the system stability is absolutely depended on the Network. This paper discussed how to anti ARP attacking. The method discussed in this paper is based on TCP/IP.