The embodiment of the invention discloses a data synchronization method and device, a mobile terminal and a storage medium. The method comprises the following steps: when a target application accessesa network, broadcasting a first user name of the target application; Receiving at least one return message for broadcast, wherein the return message comprises at least one piece of encrypted application synchronization information; Determining a decryption secret key based on the first user name, and decrypting the at least one piece of encrypted application synchronization information accordingto the decryption secret key; And synchronizing the data of the target application according to the application synchronization information obtained after decryption is successful. By utilizing the embodiment of the invention, the security risk problem during data synchronization can be solved, and the data security in the data synchronization process is improved.