The present invention provides a method and apparatus for acquiring an identity identifier of a terminal and a terminal. The method includes: configuring corresponding relationship information about a conventional user identity identifier and an access identifier (AID) of a terminal in a communication system, with the AID being a unique identifier allocated to a terminal user by the communication system; and when the terminal accesses the communication system, carrying the conventional user identity identifier of the terminal in a signaling sent to the communication system; and the communication system acquiring the conventional user identity identifier of the terminal from the signaling, finding the corresponding AID of the conventional user identity identifier from the corresponding relationship information, and returning that AID to the terminal; and the method also can configure an access identifier (AID) of the terminal in a user identity identification module of the terminal, or configure the AID of the terminal in a protocol stack of the terminal in the manner of static address input. The present invention can achieve the separation of the location of a terminal from its identity in a packet domain network under the premise of making the least change to the conventional terminal or not affecting the conventional terminal.