Abstract: The river system plays an important role in the water supply, flood discharge and water purification process of the Taihu Lake Plain. Recently, the urbanization of the Taihu Lake Plain had developed rapidly. A series of human activities such as land-use change and over-exploitation of water resources had resulted in changes in rivers and lakes, and hydrological connectivity had been affected. Furthermore, all these lead to a series of flood and water environment problems. Taking Wu-cheng-xi-yu Region of Taihu Lake Plain as an example, this paper discussed the changes of water system structure and hydrological connectivity in the 1960s-2010s by constructing river system structure and connectivity indicators. The results show that: 11960s-2010s ,With the continuous attenuation of river system, the development coefficient of the river network density and surface rate in Wu-Cheng-Xi-Yu Region decreased by 22.94% and 25.09% and 22.35% respectively, and the complexity of the river network decreased sharply. Among them, the attenuation degree of the river network in Wu-Cheng- Xi region was greater than that in Cheng-Xi-Yu Region. From 1960 to 1980, average hydrological connectivity of the region was 0.89. Average hydrological connectivity of 1980-2000 period fell to 0.82. Average hydrological connectivity returned 0.91 in 2000-2016, which showed a trend of increasing first and then decreasing. Hydrological connectivity between water stations has increased since the 1990s. 3The attenuation of the river structure and the artificial hydraulic regulation artificial hydraulic regulation made the hydrological connectivity decline. And this study will provide support and reference for the utilization and protection of river system in the plain area.