In order to improve maintainability and expansibility of software, reduce the complexity of protocol development, based on the statechart theory of Unified Modeling Language (UML), this paper analyzes the master side of IEC 60870-5-104, abstracts and defines actions, events and states; designs the statecharts of protocol logic based on the hierarchy and parallel characteristics and implements the software using Qt state machine framework. The results show that the hierarchy structure of statecharts is distinct, the logic is clear, every function model is independent of each other, and the coupling is reduced; programming implementation using Qt state machine framework is easy, showing it is a good solution. This kind of analysis and implementation method has also good reference value to the development of other complex communication protocol.