Socioeconomic development has been accompanied by expanding environmental degradation in northwestern China where water is scarce for climatic reasons. Water is a significant constraint on economic development and eco-environment protection. The conventional approach to meeting water-use needs has focused on human water demand. The ecological water requirement has been neglected, which has resulted in many problems in this region. To maintain sustainable development in arid area of northwestern China, water resource management will not only have to incorporate straightforward technological efforts but must also respond to the problems and benefits caused by the evident links between land use and water, between upstream and downstream regions, and between water and ecosystems. As attention has turned increasingly to eco-environmental security, a better understanding of ecological water demand is required. This is what this approach is all about. Based of the overview of the progresses and challenges of ecological water demand approach, this paper addressed the function of ecological water in water cycle in the study area. To balance water for humans and nature and secure the ecological water demand, some strategies have been suggested including potential vegetation prediction, productivity of green water increase and virtual water strategic application.