A method for establishing an identity management trust, and an IDentification Provider (IDP) and a Service Provider (SP) are provided in the present disclosure. The method comprises: after receiving an access from a user, an SP determines whether an IDP to which the user attaches is located in a trust domain of the SP (S102); if the IDP to which the user attaches is not located in the trust domain of the SP, the SP inquires of an IDP in a local trust domain about the IDP to which the user attaches (S104); if the SP receives information of the IDP to which the user attaches, wherein the information is returned by an IDP in the local trust domain, the SP adds the IDP to which the user attaches to a temporary trust list to establish a trust for the IDP to which the user attaches (S106). The present disclosure can establish a trust relationship between an SP and any IDP in case of adding or not adding extra devices, ensuring the user to obtain desired services after logging on for one time.