Abstract: Using the methods of the field data analyses, the relationship between the bank-full discharge in the tail channel and the flow-sediment is studied.The research results show that the bank full discharge has decreased from 6 000 m³/s at the beginning of the formation of the flow river to 3 000 m³/s in the early of 21th century.The bank-full discharge has double memory effect, that is, the strongest memory lasts nearly two years with the short-term effect, and the deeper memory lasts nearly six years with the long-rang effect.The incoming flow is much bigger and the incoming sediment coefficient is more smaller, so the bank-full discharge become much bigger, and contrarily, the bank-full discharge become much smaller.If the bank-full discharge maintains 4000m³/s, the annual incoming flow must be bigger than 23.3 billion m³, the incoming flow in annual flood season is bigger than 14.1 billion m³, and incoming sediment coefficient in the flood season is about 0.03.The regulation of the flow and sediment of Xiaolangdi reservoir should be made continuously for more than 5-6 years, and will bring good effect During uniform controlling water, daily the minimum discharge in the flood season should be confirmed at Lijin station, it will maintain definite bank full discharge in the tail channel.