In August 2004,there was a strong rainfall process in the middle reach of the Yellow River.According to the flood control scheme,high sediment concentration discharging was made by operating the Xiaolangdi Reservoir.When the flood traveled towards the river mouth,it had the characteristics of high sediment content,quite larger increase of peak discharge at Huayuankou Hydrologic Station and smaller decrease of peak discharge during propagation after the Huayuankou Station.After a series of investigation and analysis,it was thought that the main reason was the resistance of high sediment content was much smaller than that of its previous clear water,which had made the velocity much higher than its previous channel conveying flow.Thus,during the propagation downwards,the clear water and part of the previous channel storage water,which was in front of the peak,was continuously "squeezed" and a kind of piling up was formed.Through the analysis,the proposals were made for the future study,monitoring and regulation of the high sediment concentration flow.