Automatic registration system of IP telephone of IP-PBX

The invention discloses an automatic registration system of an IP telephone of an IP-private branch exchange (IP-PBX). The system is characterized by comprising an automatic registration server and an IP telephone automatic request session initiation protocol (SIP) registration client of an IP-PBX system, and a dynamic host configuration protocol (DHCP) server needing third-party supported option66. The system can effectively fuse user number management and IP telephone registration on the IP-PBX system together; any configuration on the IP telephone is not needed, namely the telephone is automatically registered after power on or restart, and the related configuration information of the IP telephone is automatically acquired; and a user can immediately dial the IP telephone, so the problems of telephone registration and number management are effectively solved.