According to the characteristics complexity of the middle and lower reaches of the Beijiang River, the flood routing coupling model including the Xin anjiang model(3 components)and unsteady flow numerical computation model is established.

Contrary to the social-economic development of the middle and lower reaches of the Hanjiang basin, which is almost in the territory of Hubei province, quality of the water in this basin becomes worse and worse.

Based on scientifical planning of all kinds of protection forest in the middle and lower reaches of Nen River and many years studying in multiplots and multifactors,was got the result:in control of soil and water losses,surface runoff,sand content and abrasivity reduced by 42.

On the support of GIS technology, the author build ecological security database using conventional maps and statistical data as data resources and establish the ecological security assessment model on the basis of quantities factors and analysis, in order to assess the ecological security condition in the middle and lower reaches of Hanjiang River Basin.