Disclosed are a communication device having a base station function of a Digital Enhanced Cordless Telecommunications (DECT) cellular system, and a communication system. The communication device includes an IP phone and a DECT adapter. The IP phone is connected to the DECT adapter, to form a base station; and the DECT adapter is configured to wirelessly communicate with at least one cordless handset via DECT, so as to register information of the at least one cordless handset with the IP phone. The present application enables the IP phone to be externally connected to the DECT adapter to support a DECT mode, so that the IP phone possesses a base station function of a DECT cellular system. It is not required to deploy multiple different systems. Such an IP phone and other base stations can form a Multi-Cell DECT system, expanding the coverage of a DECT signal.