The Yellow River basin is located in arid and semi-arid region of the northern of our country. In here the water resource is poor. The per capita water resource is only 1/3 of the average national level. The forest coverage rate is only 6%. It is 50% of the average national level. Water and soil erosion are serious. On the Middle and Upper of the Yellow Rive, the soil erosion modulus is generally above 5 000 t/(km~2a). The sand content of the Yellow River occupies the first in the world. Average sand content of many years have reached 33 kg/m~3. The reduction of water resource quantity and Increase of demand year by year have caused a series of environmental questions, such as the land desertification, the sandstorm and the Yellow River waters deterioration, etc. Project of Water Diversion from the South to the North Via the Western Course is transforms some water from Changjiang River, Lancangjiang River, Nujiang River basin of water yield plentiful to the Yellow River. The amount of water yield 17 billion m~3.The water amount of irrigation among them is used in agriculture, forest, animal husbandry occupies 55% of water quantity. It can increase vegetation, controlling water and soil erosion and contain the soil desertification. It can alleviate the imbalance between supply and demand of the water resource of the Yellow River, and improve the water quality of the Yellow River. At the same time, they can increase the length of eroding of the downstream river of the Yellow River and reduce the silt to deposit. It is favorable to the stability of the downstream river of the Yellow River.