In the maintenance work of the Yangtze River estuary channel,in order to find out the reasons for the damage of the local renovation buildings in the upper section of the south dike,the paper carries out the a detailed field investigation and analyzes the topographic condition,hydrodynamic characteristics and hydrodynamic model of the damaged section,and gets to know main causes of the damage,i.e.,under the combined action of river regime conditions and hydrodynamic factors,the slope near the embankment turns steeper gradually,which leads to the damage. Based on this,the repair design scheme is compiled and the repair is completed with good results achieved.