Abstract: In this paper the technological conditions required to float logs across high-head dams by hydraulic means are discussed.With a hydroengineering model of 1/25 in scale, the frequence and strength of the impact made by the floating log on the flume were measured by a transducer;also measured were the depth and velocity of the flow in the flume with gradients from 5% to 13%. In the experiment the cause of aeration in the flume added with intensive rough has been studied as well. The main process of the experiment has been recorded by a video recorder.This paper gives the optimum gradient and outlet conditions for the flume of 50 meters water-head, and presents suggestions for the reconstruction of the flume at Gongzui Hydropower Station.