Data synchronization method, data synchronization system, data synchronization server and terminal

The invention discloses a data synchronization method, a data synchronization system, a data synchronization server and a terminal. The synchronization server judges the source of a corresponding digital content according to brief information uploaded by a user, and determines to only store the brief information or further store storage position information of the digital content or the digital content itself according to the source of the digital content. Therefore, data flow of data backup is reduced, the difficulty of data migration during terminal replacement by users is simplified, and the communication cost of users and the cyber source pressure on operators are reduced.