The Core of the problem is just the economic justice between urban and rural areas,the economic unjustice between the urban and rural areas not only has historical cause,also present cause.

Economic justice is closely related to the soicialist harmonious society.

Furthermore, under the condition of socialist market-oriented economy, economic justice becomes even more important, which brings about social & legal justice .

Economical justice is a quite lofty moral ideal that human-being pursuing, it penetrates in the everywhere of people s social life, especially in the economy field.

In this paper we study a mathematical model of population shifting, and propose a optimal disision model for social economic classes construction.

The social justice on behalf of quality of life, including the justice of economic rules, political rules and cultural rules, dominates the distributions of economic, political, and cultural interests of the mass, and proves to be a real and all-round reference to modern life which people seek after.

The author discusses the connotation of the economic justice and the intergenerational economic justice and their inner link,and elaborates the serious influence of the natural resource failure and deterioration of environment to the human existing and sustainable development.