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

The invention provides a data synchronization method. The data synchronization method includes the steps of receiving running state information, transmitted by a terminal, of any system in multiple systems of the terminal; judging whether any system breaks down or not according to the running state information, stored performance information of any system of the terminal and a failure predication standard; when it is judged that any system breaks down, transmitting warning information to the terminal for enabling the terminal to prompt a user of the terminal to select whether data of any system are synchronized to a cloud server or not according to the warning information; receiving and storing the data, transmitted by the terminal, in any system. Correspondingly, the invention further provides a data synchronization device, the terminal, the cloud server and a data synchronization system. By means of the technical scheme, the data of the system can be synchronized to the cloud server and are synchronized to other systems of the terminal through the cloud server, and losses of the data of the user are accordingly avoided; in this way, even though the system breaks down, the user can still use the data in the terminal, and the user experience of the user is improved.