Abstract: The using of design patterns in EMS system can decrease the complexity and improve the efficiency of system development. By analyzing Singleton pattern, Adapter pattern, Observer patter, the paper discussed their architectures in detail. In advanced, it can provide a theoretical guide to realize system functions with these patterns. In the end, it analyzed why and how to use these patterns to EMS system. The application of design pattern in EMS has been proved to be an efficient way to enhance the quality of EMS.