A data synchronization system and method. The method includes that when a change happens in a source application, data is collected from a source application based on a target application subscribing the source application and collection data is transmitted to the target application or is directly inserted to target database. The system includes data collection unit and distribution unit. The present invention may realize synchronization on demand, simultaneously reduce greatly synchronous data quantity, decrease network load, and guarantee smoothness and stabilization of network. The present invention applies to data synchronization of enterprise internal/external data systems, telecommunication networks, etc.