The Comparative Advantage Theory of David Ricardo is constructed on a series of assumptions including perfect competition and constant returns to scale. Under these assumptions, division of labor should be on the basis of Comparative Advantage Theory. Agglomeration derives from such basic conditions as increasing returns to scale, trade costs, flow of productive factors and imperfect competition. When agglomeration effect is taken into consideration, the comparative advantage cannot fully determine the division of labor and the trade pattern of a country or a region, while He agglomeration advantage can decide the industrial layout and division of labor, which provides a new explanation to Leontief Paradox in the traditional international trade theory. The fact that manufacture concentrates in East China indicates that in a country, agglomeration advantages play a more important role than comparative advantages. Accordingly, wheather in western development or in Northeastern reviving movement, development of industries can＇ t depend on comparative advantages. Instead, we should focus on improving factor productivity and fostering agglomeration advantages