Abstract: Dam is an effective utilization and regulation method for water resource, which has made an important contribution to social and economic development. Dam changed river natural attributes, being the important driving force for the downstream landscape and its ecological system services. Dam changed the spatial and temporal distribution of regional water resources, which generated the corresponding water effects at different scales and different levels: (1) Dam caused physical, chemical, and biological changes of the river, from downstream to estuary. These changes mainly took place in river channel, hydrological and species flow, etc. (2) The changes of the surface water and groundwater affected the riparian zone, irrigated area, flood plain and horizontal region. Reduced water supply ability had great influence on the underground aquifer and the wetland. The interaction between the main stream and tributaries and lakes was blocked, influencing the transmission and exchange of water. (3) The change of water environment influenced the degree and direction of social and economic development, and the downstream land use and land cover changed correspondingly. Ecosystem services had been realized by cooperation of geographic process, biological process and social economic development. Dam changed the water, energy and material cycling process, which would have longterm and farreaching influence on the maintenance of regional ecosystem services. Dam strongly changed regional ecosystem services network’s stability and development through affecting the downstream primary and secondary effects.