The marginal field has successfully developed and implemented a new type riser system in the East China Sea,its development strategy and construction experience has a certain reference for the development of follow-up similar marginal fields. The characteristics of this new type riser system are analyzed,and the difficulties in welding and installation are introduced,such as welding operating area,fitting up,and riser lifting and overboarding,and so on. The key technologies,operation problems and solutions of this new type riser system in offshore welding and installation are summarized.