From August to October,2003,there was a 50-day rainfall process in the river basins of Jinghe,Weihe,Beiluohe and Sanmenxia-Huayuankou Reach,so as to result in an infrequent autumn flood on the middle reach of the Yellow River.In order to increase the flood carrying capacity in the main channel of the lower reach of the Yellow River and scour it entirely,and mean- while to explore the way of joint regulating the reservoirs of Sanmenxia and Xiaolangdi,the YRCC made the second sediment- runoff regulation from 6th to 18th September,2003.This paper analyzed the flood and sediment regime at the main cross-sections and the silt accumulation problem in the lower reach of Yellow River.The results show that there were about 2.65 billion m~3 wa- ter and 0.456 billion t sediment going through the Huayuankou Hydrometric Station,about 2.714 billion m~3 water and 1.202 bil- lion t sediment were sent to the sea,while the lower channel was scoured.The flood carrying capacity in the main channel of the lower reach increased by 150-400m~3/s and the stage at 2 500 m~3/s decreased by 0.04-0.23 m.