the water used in the production process of an agricultural or industrial product is calledthe "virtual water" contained in the product, and virtual water strategy means countries or regions whose water is scarce achieve their water security and food security by importing waterintensive products from those whose water is abundant. As an attractive instrument to water scarce countries, virtual water has received more and more attention and been applied to relieve the pressure on the nation's own water resource and solve food scarcity. The paper introduced the concept of virtual water first, then the framework of virtual water research and in advance , then illustrated the virtual water content calculation methods of kinds of products. As a case, the paper calculated the virtual water consumption of the very four provinces according the actual situations and the accessibility of data in northwest China in year 2000. Some discussions were conducted, especially the policy implications of virtual water strategy for northwest arid China. The paper ended with some summaries and suggestions such as strengthening the virtual water research, establishing the regional policy supporting system, innovating the water management mechanisms, applying the virtual water strategy in some potential regions gradually, and so on.