A method and a system for backing up terminal data are disclosed. The scheme is used for solving technical problems that existing ways for backing up terminal data have a low duplicating efficiency and resources are wasted seriously. The scheme creates a terminal index table to maintain data information in a terminal device; when the terminal device newly creates or modifies data contents, information of the index items in the terminal index table and corresponding data contents are sent to a network server; the network server also creates a server index table corresponding to the terminal index table, and the network server stores or deletes data contents of the terminal device according to information such as types and numbers of index items. The scheme can back up terminal data rapidly and simplifies the check procedure, thereby saving memory resources of the terminal device and improving backup efficiency.