Abstract：As one of the main theories of regional economy, grads theory attracted a good many of economists' attraction after its naissance in 1970s. It is growing more and more stronger day by day.
Grads transfer theory originally came from Vernon's industrial production stage of the life cycle theory. The theory holds that industrial departments and various industrial products are all in different life-cycle stages of development. They're the stages of innovation, development, maturity and decline. Thereafter, the Prince and Hexizhe validated strengthened and developed the theory. Regional economists introduced this theory to regional economics, resulting the transfer regional economic development gradient theory. The theory believes innovation activities are the determining factors of the level of regional development gradient, and most innovative activities are in high gradient areas. With the passage of time and changes in the life cycle stages of production, activities gradually transfer from the high gradient areas to the low gradient regions, and this gradient transfer processes primarily through multi-level expansion of the city system.
The Grads Theory was introduced to China in 1980s, and is holding more and more attraction. It has mainly gone through Traditional Grads Theory (in narrow sense), Inverse Grads Process Theory, generalized Grads Process Theory, and so on. Traditional Grads Theory mainly holds the idea that economic technology is surely developed with different steps, and objectively causes the economic grads, then the productivity transformation happens from the high grads to the lower grads. Inverse Grads Process Theory supports the traditional grads theory and further come up with the idea that underdeveloped region also exerts its own advantage, forms higher industry distribution grads, inversely transfers to the traditional centre and drives the middle regions' development. Based on the whole system that contains nature, economy, soiety, human, ecosystem and institution with complex domestic relationship, Generalized Grades Process Theory starts a new stage.
This theory, as its practicability and validity, played a very important role in establishing our countries' economy strategies. Gradient transfer theory also has some limitations, which are mainly hard to scientifically divide gradient, it is possible to cause solidification of each region and the more and more serious development gap between regions.
This paper takes the development process as the clue to summarize the representative points in different times and gives comments on the above theories in the end.
