IMS network access method using existing equipment

The invention discloses an IMS network access method using existing equipment. A communication network (100) is described and allows the existing equipment to get access to an IMS network (108). The communication network (100) comprises an exchanging system (104), the IMS network (108) and a non-IMS network (110). The exchanging system comprises a user data base (106), and identities of an IMS user using the existing equipment are prepared in advance. The method includes the steps that in the operating process, a calling party (106) makes a call through the existing equipment (102); the exchanging system receives the call and gets access to the user data base according to identifiers of the calling party (such as a phone number and a URL) so that whether the calling party is the IMS user or not can be judged; if the calling party is the IMS user, the exchanging system will route the call to the IMS network, and if the calling party is not the IMS user, the exchanging system will route the call to the non-IMS