Under the dual effects of natural geographical climate change and human activities,the pattern of river system in plain river network has changed greatly. Based on the river network data in the 1970s,1980s and 2010s,the river quantity,structure and connectivity were selected as indicators. By employing GIS and RS methods,the characteristics of the indicators were analyzed in terms of the spatial and temporal evolution, exemplified in the the river network of Yandu district,the typical area of Lixiahe region in the lower reaches of the Yangtze River. The results showed that: (1) The river density and water area ratio of the whole Yandu district decreased steadily by 21.3% and 10.2%,respectively. The degree of river curvature was relatively small and the connectivity of river network was fairly good. The curvature and connectivity of the whole river network changed little. (2) There was a temporal-spatial variations in the river network change of Yandu district. The decay rate in the low urbanization period (1970s ~ 1980s) was greater than that in the high urbanization period (1980s ~ 2010s) ,especially for the low level of urbanization areas. The degree had been changing dramatically in the high level of urbanization areas. (3) There was variability among different river grades. Impacts of urbanization on river network demonstrated an order of the lower grade(IV) rivers,followed by the higher grades(I-III) rivers. The number of lower grade rivers decreased constantly at a strong changing intensity,while the higher grade rivers demonstrated minor changes in river quantity,but a gentle increase in river area and length.