Since the 1970s, it has been a relatively-stable evolution pattern in the south branch at Changjiang estuary, where the evolution is well regular. The pattern’s formation relates to the boundary conditions of the south branch and the flow and sediment into the south branch. Based on the topographical data and the runoff and sediment characteristics over the years, first of all we expatiate on the evolution regulation of the south branch and the interaction between the sand bodies and the channel; then we analyze the influence from the artificial engineers and the runoff and sediment; and lastly, we generalize the river channel evolution pattern.