A base phone and additional phone implementation method, and an Internet Protocol (IP) terminal. The implementation method includes acquiring, by the IP terminal, a group address, group-sending, by the IP terminal, a base phone query message according to the group address, and determining whether a base phone feedback message is received, and when the IP terminal receives the base phone feedback message fed back by a base phone, marking the IP terminal as an additional phone, and otherwise marking the IP terminal as a base phone, and registering with a server, and according to the implementation method the base phone and the additional phone are set up using IP terminals, which avoids disadvantages of a lack of security protection and proneness to theft when an analog phone is connected in a manner of physical parallel connection of copper cables, and therefore improves security significantly.