As the new century enters,the basic structure of Chinese regional economic development is speeding up the North-westward migration.Therefore,constructing economic belt around Yellow River is necessary to make the emphasis of national economy in China's North-westward migration. In this article,it is complex for economic belt to form with scale invariance or comparability,that is,the formation of economic belt has the characteristic of fractal,and enterprise of industry and commerce is the fractal unit which builds the economic belt.From Zipf dimension,the growth of economic belt around the Yangtze River is more mature than around the Yellow River.Thus,this article takes economic belt around the Yangtze River for instance,makes use of DLA fractal model whose shape is similar to foursquare star,and understands this unbalanced process dynamically and analyzes the formation mechanism of economic belts around the two rivers in another way.