Abstract: The river network structure changes much with the development of urbanization in the coastal area of Southeast China.As a result,a series of ecological problems such as the flood and waterlogging disaster,drought and the deterioration of water quality occur.We take the Southeast Yin plain area in the coastal areas of East Zhejiang province as an example in this paper.With the support of GIS technique,and the aerial pictures as main information resources,the changes of river network in the study area are discussed by analyzing the change of river structure due to urbanization adopted measurement,the statistics of river gradation and the map overlaying.Besides,the correlation between the urban expansion and the river network evolution is studied,and the trends of river structure changes under the present urbanization in the study area are qualitatively forecasted.Based on these,the measures to avoid the trends are discussed,that is,the existing riverways should be reserved as much as possible in the course of urbanization,especially the small and medium river channels.The restoration of river network structure and functions should be attached much importance so as to improve the urban water quality and water environment.The study will provide reference for the protection of river network during urbanization in the coastal area of Southeast China.