A method for notifying a network domain and an Access Point (AP) are disclosed to overcome the problem that User Equipment (UE) entering the AP cell is notified but a UE leaving the AP cell is not notified. The method includes: the AP receiving a service request message sent by UE; and inserting a preset voice data packet into a user plane before a conversation to indicate the user of the UE a network domain that covers the UE currently, if it is determined that a current signaling connection is a Circuit Switched (CS) connection according to the service request message.