Abstract: The analysis of river run-off characteristic and flood behaviour of North River in Peal River basin is presented in this paper. Based on the practical experience in the planning and design works, a summary about the operation types of run-off-river hydroelectric plant in the trunk stream of North River and corresponding application coditions is carried out. A case study is also presented to express the necessity of studies on operation rules of run-off-river hydroelectric plant by comparing the benefits among the different rules.