Abstract: Flood diversion project is one of the most important drainage facilities in Dongting Lake area, especially in the estuary areas of the Xiangjiang River, Zishui River, Lishui River and Yuanshui River into the Lake. Due to the impacts of the changed relationship between Yangtze River and Dongting Lake and human activities, the sediment deposition is getting more serious in the three distributaries of Changjiang River to Dongting Lake and the Dongting Lake area, leading to a rise in flood level under the same flows, longer duration at high flood stage and further a reduction in gravity discharge and running efficiency of the flood diversion projects and more frequent risk occurrence of flood diversion embankment, which seriously impacts the operational safety of the project. This paper takes typical Chongliu diversion project for high water level as a study case to compare the running effects of the project under different the river-lake relationship in the 70's of 20th century and the beginning of the 21st century and the difference causes. According to the analysis results, the corresponding countermeasure of constructing a pump station for the flood diversion project is put forward. For the pump station, the flood drainage effect is assessed.