The effect of urbanization on the stream structure and connectivity has been a hot topic nowadays.At the present,fast urbanization has caused many enviromental problems,such as the decreasing of river numbers,rivers unconnected,water quality worsening,and frequent flood.The Qinhuai River watershed,mainly located in Nanjing City,Jiangsu Province,China,could serve as a good example.Two remote sensing images in 1979 and 2006 in mid-lower reaches of the Qinhuai River were processed and classified for the analyses on the spatial and temporal characteristics of underlying lands,which were the result of urbanization.The river systems were extracted based on the topographic maps in 1980s and 2009,and the influence on the stream structure and connectivity was discussed using a combination of stream grading and structure analysis methods on the river corridor in landscape ecology.Results show that: (1) Urban land has increased 9 times by 84.54 km²,and a large area of forest land has been transformed into urban land.Besides,paddy and dry land area were also decreased.Expanding of the urban areas of the city has invaded many other lands.(2) Length of the river has been decreased by 41% and the main river channel of the catchment are broadening.The stability of river has been declining and composition of the river system network was getting simpler.The stream stucture was developing from a complex model to a simple one.(3) Parameters of the river connectivity were both decreased.This explains why the rivers were not as well connected as 30 years ago and flood risk of this area current is high.