Using the field measurement data of underwater topography and the hydrological data, the river-bed evolution of South Branch in the Yangtze Estuary is analyzed, and the evolution process, characteristics and mechanism are discussed. The results indicate that the river-bed of South Branch remained stable in the past decade generally, and has some changes as follows: 1) The import section of the Baimao sand shoal north waterway deposits, and the south waterway erodes; 2) The main channel of South Branch below the Qiyakou erodes in the north and deposits in the south; 3) South of the Xiabiandan sand shoal erodes in the upstream and deposits in the downstream; 4) The heads of sub-Xinliuhe sand shoal, Xinliuhe sand shoal and Zhongyang sand shoal retreat obviously; 5) The volume of river channel is increased. The evolution characteristics have a close contact internally and the river erosion-accretion shows a top-down transfer process. The main driving factor of the recent erosion-accretion evolution is the flowing sediment in North Branch, and the other two factors are ebb-tide advantage flow and the silty river-bed. These factors will still exist, therefore the river-bed of South Branch will continue the recent evolution trends.