Abstract: In this paper,based on the self adjusting theory of alluvial channel,the impact of the large scale hydroelectric projects on the Inner Mongolia reach of the Yellow River is analyzed.The reason of recent change of the river characters and the constraint relationship between the freedom of adjusted river bed and the energy allocation and dissipation of the river system are researched.The suggestion for the operations of large scale reservoirs on the upper reach of alluvial river are presented from the relationship of harmonized river with mankind activeties.