A realization method for participating in a predefined group session, the method comprising: receiving by a controller function server a group session participation request sent by a terminal, wherein the group session participation request carries a conversation identifier and a contribution identifier; and sending the conversation identifier and the contribution identifier to other terminals which participate in a predefined group session subsequently by the controller function server; characterized in that, the method further comprises: receiving, by the other terminals, the conversation identifier and the contribution identifier and updating, by the other terminals, a local conversation identifier and a local contribution identifier to be the ones received by each of the other terminals; and in that, after the controller function server receives the group session participation request sent by the terminal, the method further comprises: if the controller function server determines that the terminal is a first terminal that participates in the predefined group and the group session participation request received by the controller function server is of a participative group type, storing the conversation identifier and the contribution identifier contained in the group session participation request by the controller function server, and, if requesting to participate in the predefined group session, the other terminals send a group session participation request according to the updated conversation identifier and contribution identifier so as to participate in the same group session. receiving by a controller function server a group session participation request sent by a terminal, wherein the group session participation request carries a conversation identifier and a contribution identifier; and sending the conversation identifier and the contribution identifier to other terminals which participate in a predefined group session subsequently by the controller function server; receiving, by the other terminals, the conversation identifier and the contribution identifier and updating, by the other terminals, a local conversation identifier and a local contribution identifier to be the ones received by each of the other terminals; and in that, after the controller function server receives the group session participation request sent by the terminal, the method further comprises: if the controller function server determines that the terminal is a first terminal that participates in the predefined group and the group session participation request received by the controller function server is of a participative group type, storing the conversation identifier and the contribution identifier contained in the group session participation request by the controller function server, and, if requesting to participate in the predefined group session, the other terminals send a group session participation request according to the updated conversation identifier and contribution identifier so as to participate in the same group session. if the controller function server determines that the terminal is a first terminal that participates in the predefined group and the group session participation request received by the controller function server is of a participative group type, storing the conversation identifier and the contribution identifier contained in the group session participation request by the controller function server, and, if requesting to participate in the predefined group session, the other terminals send a group session participation request according to the updated conversation identifier and contribution identifier so as to participate in the same group session.