Abstract: The Gezhouba reach ran out of the Sanxia Gorge and developed on an alluvial fan which was restricted by the rock hills of both banks,representing some complex features of fluvial geomorphology, such as channel widening or branching, main current abruptly turning and unconsequently running. The channel widenin5 seems to relate to the unequal rising of neotectonics and the differential erosion on various lithological characters for long time.The trend that the channel moves to right bank during the river evolution process and the fact that the main current near the convex bank now obviously indicated the relation ship between the evolution and unequal tilting of neotectonics, the extension of Hwangbai River alluvial fan and the flow deflecting caused by Hengliangzi. Since A.D.500 the situation that ErJiang and Sanjiang branches have had no water in dry seasons has been formed. At present, the two branches are still in declining stage.