Disclosed is a door intercom system, which is installed on a door of a community for communicating with and identifying a visitor and opening/closing the door through a network by an inhabitant among a plurality of inhabitants of the community and capable of transferring data to a system provider through the network. The door intercom system has a central processing unit (CPU) connected to a database, a dialing key module, a display module, a video and audio processing module and a network interface, respectively. In the database, inhabitant codes, network logon numbers and identification numbers of the plurality of inhabitants are stored. When the visitor inputs an inhabitant code through the dialing key module, the CPU acquires the network logon number corresponding to the inhabitant and is communicatively connected to the network through the network interface, the network being connected at the other end to the inhabitant end or the system provider through a public switched telephone network (PSTN). As such, the visitor is allowed to communicate with the inhabitant by an email or message through the display module. Alternatively, the visitor may directly communicate with the inhabitant by a IP phone or be directly identified by a VP phone.