The present invention discloses a realization method and system for participating in a predefined group session, and the method comprises: a controller function server receives a group session participation request sent by a terminal, wherein the group session participation request carries a conversation identifier and a contribution identifier; and the controller function server sends the conversation identifier and the contribution identifier to other terminals which participate in a predefined group session subsequently. By means of the present invention, a uniform identifier of a group session is configured for the terminals so that the terminals can participate in a predefined group session correctly, trace an established session accurately or initiate a same session repeatedly according to the uniform identifier, and therefore the present invention fill the gaps in the related technology.