The relative superiority was calculated and used to compare ranges of the target parameters.

Then, it gives the definition of relative superiority describing big or small interval number, and a new ranking method of fuzzy complementary matrix respectively.

Then using a interval distance formula, a relative superiority formula is given to compare any two intervals.

With the interval number reflecting the relative membership degree of fuzzy sets, the relative superiority degree was introduced for comparison of interval numbers, and a multiple fuzzy optimization model was developed, avoiding the different estimated results in optimal selection of schemes caused by different ways for calculating the relative membership degree.

Firstly,some concepts,such as interval numbers consistent reciprocal judgment matrix,relative superiority degree,etc,are given.

To make use of the EMDS(Ecologic Manage Decision System)on the ARCGIS and the priority analysis in the Watershed synthetical evaluation, this paper tries to assess the status quo of the basin entironment.

And as for the repeated cooperation,the profit-sharing scheme should follow the comparative advantage principle in which the sharing rate is determined by the comparing result of relative cos.

free trade brings ultimate benefits to us based on the law of comparative advantage.

The article puts forward some new ideas of economic development in Northwest China in 21st Century by analyzing its relative advantages and restrictive factors.