The Korean High-speed train was developed during 1996 to 2007. This development project consists of many sub-projects and the train-system includes a lot of sub-systems. In order to promote the project on planned cost and time effectively, we tried to apply systems engineering process during the whole life-cycle. The purpose of this paper is to introduce the systems engineering process applied to this project. Activities carried out in each phase such as pre-design, detailed-design, integration & verification are described.