简要介绍了软交换系统的工作原理、功能、优势、网络结构,重点介绍了软交换在昆明市轨道交通首期工程公务电话系统中的应用实例,描述了其组网情况、系统对外中继情况、系统容量、冗余机制、分布式构架、系统中运行的协议。本文给软交换技术在轨道交通公务电话系统中应用的优越性提供了很好的支持。 The working principle, functions, advantages and network structure of softswitch system are briefly introduced. The application example of softswitch in the first stage public telephone system of rail transit in Kunming is emphatically introduced. The networking situation, the system external relaying situation , System capacity, redundancy mechanisms, distributed architecture, protocols running in the system. This article provides a good support for the superiority of softswitch technology applied in rail transit official telephone system.