Abstract:This paper addresses the issue of water resources reasonable allocation & its carry capacity in Northwest China. Analysis indicates that major problem in this area is of conflict among the limited water resources, population growth, social economic development. even though water resources development is rather higher, water use efficiency is low & water saving potential is big in this area. At present, water use amount per capita is about 868m3 that is significantly higher than the averaged 434 m3 in China. In 2002, the water use amount related to the gross domestic product (GDP) of 10 000 Chinese Yuan value is high to 1 433m3, averaged one in China is only 537m3. Thus is due to present agriculture structure with high water assumption and low product. In water resources reasonable allocation, the key is of water saving of agriculture irrigation system. It is possible for present water resources to support social economic development only by water saving, change traditional economic pattern, keep eco-system protection, and find new water resources.