Abstract: River systems are the major transport channel between land ecosystem and aquatic ecosystem,but the constructed dams fragmented the river ecosystems,that can change their physical,chemical and biological characteristics.The detail effect of the dams are reviewed on the hydrological and hydrodynamic characteristics,the nutrients transportation,the structure and functions of the river ecosystem,and the corresponding measures for the ecological restoration.With larger dames as major component of the hydrological cycle,their effects on the watershed ecosystem health is increasing.We need to study their negative effects on the ecosystem and the corresponding restoration measures.