The present invention discloses a method for implementing Wide Area Centrex (WAC), wherein the long number and short number corresponding relationship of the WAC users is set and saved. The method includes: routing the call initiated by a user to a soft-switch; receiving by the soft-switch the call information the calling user sends; after determining that the calling user is a WAC user based on the calling number, the soft-switch determining the route to the called user based on the call information and completing the call. The WAC, covering the Public Switched Telephone Network (PSTN)/Public Land Mobile Network (PLMN) user and the Next Generation Network (NGN) user of different physical networks, can be implemented by using the method of the present invention without any software or hardware change to the switches in the existing network.