Abstract: In consideration of a lot of large reservoirs being constructed and fast economic and social development demands in the Changjiang River basin, the united regulation of a group of reservoirs must be adopted so as to control flood, to develop economy and to conserve ecological balance. In this paper according to the conditions of large reservoir construction and their features, the capacities of large reservoirs in future 10 years are forecasted, and from the aspects of flood control, benefit in water resources and so on, the ability of reservoir regulation and existing problems are respectively analyzed. The analytic result shows that though there are a number of constructed reservoirs, the reservoirs water capacity that can be directly employed to regulate is still finite due to a large quantity of water in the Changjiang River. From the point of view of regulating capacity and running mechanism, the united regulation can be effectually applied to flood control and emergency diversion. The reservoir regulation for ecology, drought in large area and mitigating sea water invading in estuary is only in the exploring stage. To solve the problems of drought, ecology and sea water invading, etc., integrate measures include reservoir regulation must be used.