This paper studies the floodreleasing and energy dissipation of the overflow dam at Lechangxia water control project which is located in a narrow river valley. The floodreleasing safety of the overflow dam therefore is a critical technical issue as it has large water head drop and the discharge per unit width of the dam is large, and moreover, the tailrace exit of the hydropower station is in the vicinity of the dam. Based on hydraulic model tests, the hydraulic property of the overflow dam is improved and hence problems of floodreleasing and energy dissipation and scour protection are solved in this paper by optimizing the layout and configuration of overflow weir and both the contracted sidewalls as well as piers and flip buckets.