A method for sending a large message mode converged IP messaging, CPM, message to a group, wherein the method is used for a sender CPM client to send the large message mode CPM message to a target group, comprising: sending a session invitation message of the large message mode CPM message by the sender CPM client, and after receiving the session invitation message, sending the session invitation message to each receiver address in the group by a CPM controlling function entity; receiving the session invitation message and carrying out a media negotiation with the CPM controlling function entity by a receiver CPM client, and carrying out a media negotiation with the sender CPM client to determine a media transmission link between the sender CPM client and the receiver CPM client by the controlling function entity; and/or receiving the session invitation message and carrying out a media negotiation with the controlling function entity by an inter-working function entity, and carrying out a media negotiation with the sender CPM client to determine a media transmission link between the sender CPM client and the controlling function entity by the controlling function entity; sending the content of the large message mode CPM message to the receiver CPM client and/or the inter-working function entity via the media transmission link by the sender CPM client; and initiating a flow to end the session of the large message mode CPM message by the sender CPM client, the controlling function entity, the receiver CPM client or the inter-working function entity; wherein the method further comprises: when receiving the session invitation message, obtaining, by the CPM controlling function entity, a receiver address according to a group member list carried in the message body of the session invitation message if the receiver is a temporary group, or obtaining, by the CPM controlling function entity, a receiver address from a document server if the receiver is pre-defined group. sending a session invitation message of the large message mode CPM message by the sender CPM client, and after receiving the session invitation message, sending the session invitation message to each receiver address in the group by a CPM controlling function entity; receiving the session invitation message and carrying out a media negotiation with the CPM controlling function entity by a receiver CPM client, and carrying out a media negotiation with the sender CPM client to determine a media transmission link between the sender CPM client and the receiver CPM client by the controlling function entity; and/or receiving the session invitation message and carrying out a media negotiation with the controlling function entity by an inter-working function entity, and carrying out a media negotiation with the sender CPM client to determine a media transmission link between the sender CPM client and the controlling function entity by the controlling function entity; sending the content of the large message mode CPM message to the receiver CPM client and/or the inter-working function entity via the media transmission link by the sender CPM client; and initiating a flow to end the session of the large message mode CPM message by the sender CPM client, the controlling function entity, the receiver CPM client or the inter-working function entity; wherein the method further comprises: when receiving the session invitation message, obtaining, by the CPM controlling function entity, a receiver address according to a group member list carried in the message body of the session invitation message if the receiver is a temporary group, or obtaining, by the CPM controlling function entity, a receiver address from a document server if the receiver is pre-defined group.