Cross-center group instant messaging method and system

The invention discloses a cross-center group instant messaging method and system. The method comprises: deploying cross-center group communication systems at a first center and a second center respectively; the first center creating a group through the group management module, generating group change information and sending the group change information to the second center through the cross-domaincommunication module; adding users to a group through a group management module, generating group user change information and sending the group user change information to a second center; generatinggroup message change information and sending the group message change information to the second center when the user adds the message in the group through the message receiving and sending module or the file receiving and sending module; and the data synchronization service module of the second center synchronizing the group information, the group user information and the group message informationaccording to the group cha