In view of the particularity of intelligent mobile applications and its data offline synchronization problems, we put forward a scheme of data synchronization, using JSON technology to design data exchange protocol and the SQLite database to store the mobile terminal offline data, using the conflict detection algorithm based on time stamp to improve the accuracy of synchronization as well as the incremental synchronization mode to ensure the efficiency and accuracy of synchronization. This proposed method is applied to an intelligent security system, and the results show that the efficiency of offline data synchronization based on JSON is about 8% higher than that of the traditional XML based scheme.