Authentication method and device for PBX having access to IMS

The invention discloses an authentication method and device for a PBX having access to an IMS. The method comprises the steps that an ICSCF receives a calling INVITE message which is generated by an MGCF and carries virtual relay information; the ICSCF initiates a search request of an SCSCF to an HSS, and a calling subscriber is attributed to the SCSCF; the ICSCF receives corresponding relation information between the calling subscriber and a relay of the calling subscriber, and the corresponding relation information is returned by the HSS; the ICSCF conducts continuation of the attribution SCSCF on the calling subscriber according to the consistency between the virtual relay information and the corresponding relation information between the calling subscriber and the relay of the calling subscriber. According to the authentication method and device for the PBX having access to the IMS, by means of the comparison between an MGCF-Trunk field and an HSS-Trunk field, authentication of the TDM-PBX having access t