Abstract: Leaving the narrow valley near Zheng Zhou,the Yellow River flows over an alluvial fan. As a huge amount of sediment was transported into the sea, the river mouth extended into the sea at a rapid rate, silting up the river bed and causing breaching of the bikes and avulsion of the river, and the estuary often changed its position. As a result of this kind of river development process, the old beds of the Yellow River, like branches of a big tree, can be found almost everywhere on the great North-China plain. The cyclical process of the estuary development-rerouting-extending-rerouting, taking place now, is an epitome of the estuary development in the past but on a rather big area. Now, the extension of river mouth is the direct cause of aggradation of the river bed above the point of estuary pivot. Fundamentally, the aggradation is due to the tremendous sediment load resulting from the soil erosion in the upland area of the Yellow River drainage basin.