Abstract: The change of river-lake relation is one of the most important factors affecting the flow and sediment environment in the Dongting Lake area. This has a great influence on the safety and development of lake shipping. On the basis of the hydrological and topographical field data, this paper studies the variation in the characteristics of the water-silt environment and then analyzes its influence on the lake channel. The following results were observed that after the project impoundment: ① The mean monthly discharge in dry seasons tends to decrease, the siltation in the lake area slows down and even scours, the low water level at the lake outlet rises to a certain extent, the water surface gradient in the lake tends to decrease; ② The decrease of incoming sediment causes the channel incision, and the rise of low water level at the lake outlet increases the channel water level, the channel is therefore deepened. The river-lake relation is overall positive factor for the lake channel and the benefits for the Xiangjiang channel are more than that for the Kaihu channel.