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: receiving a service request message sent by UE; and inserting a preset voice data packet before a conversation to indicate 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.