This invention discloses a method for synchronizing a plurality of devices, including: obtaining, by a first device, an extended address of an informational node of a plurality of informational nodes of a second device, the plurality of informational nodes arranged in a hierarchical tree structure; and utilizing the extended address to locate the informational node amongst the tree structure to enable synchronization of the informational node; wherein the extended address includes a hierarchical location of the informational node. This invention further discloses a system, client and server for data sync, and the folder-level data sync can be implemented by using the method of this invention.