Water is the fundamental natural resources and the essential element of ecosystem & environment. In China water resources in per capita is scarcity and its spatio-temporal variation is great. Generally water & land resources spatial distribution is not compatible, and ecosystem is vulnerable in China. In the past decades China have been making a great progress in social and economy development, meanwhile the conflict between water demand & supply is going be seriously. In some populous & developing regions the proposals of inter basins water transfer are been pronounced. Sustainability and harmoniously living in nature is going to be the guide line and objective of human been. On one side in macro scale the national development demand water resources deployment, on the other side the water transfer would produce far-rang & long-term impact on ecosystem and environment. So the inter basins water transfer would be the controversyOn that background, this thesis is going to summarize the experiences and lectures of inter-basins water transfer, study the key issues and then practice the approaches in case study. The paper analysis the bilateral relationship between inter-basins water transfer and ecosystem & environment, point out that the intention and goal of transferring water is going to mitigate the deterioration of ecosystem and environment caused by competitive water utilization in water shortage region. The thesis applying three balancing of water resources supply-demand analysis, parsed the water resources situation in the shortage region, researched the rational water resources deployment, guide lined the approaches of integrated water resources management combining with divided water and local water resources. This thesis estimated the inter-basin water diversion effects, discussed the water price calculation mechanism. Paper established the general evaluation & optimization method in laconic, intuitionistic, flexible style to lay out the inter-basins water diversion schemes. Based no the theory and method of system analysis, this thesis figured out that the social security system composed by law, government, market and the public participation is the essential precondition for construction, implementation and administration of the inter-basin water diversion project.Taking the project planning phase as work platform and utilizing the technique approaches hereinbefore, the thesis quantitatively analysis the impact of water diversion on each system of economy, society, resource and environment. Applying the conception of entropy and the