An important transition area of river ecosystem, riparian zone is the most active area with material transportation and energy conversion in the river bank environment. Riparian zone as an important part in the river ecosystem, is a hot topic in the study of river ecology around the world. This paper makes a review on the researches in the definition, scope, characteristics and functions of the riparian zone, and presents the progress and results of theoretical researches in this regard. The paper provides a more extensive theoretical basis for further study.