Abstract: The process of urbanization tends to have phases. Urban expansions on different land use scales or in different regions have different phases, and their interactive mechanisms with economic development are significantly different. In this paper, 21 cities at prefecture level or above in Guangdong Province are taking as the study cases. According to the changes of their niche values in 1995-2010, the 21 cities are divided into four grades. Selecting the built-up area expansion as the indicator of urban expansion, the GDPs of the secondary and tertiary industries as the indicators of economic development, Kuznets curve, Logistic model, cointegration and Granger causality tests and decoupling theory are used to analyze the relationship between urban expansion and economic development. Four methods are combined to study the relationship between urban expansion and economic development in cities of different grades from different perspectives. The results show that the assumption of the relationship between urban expansion and economic development should be fully market-oriented, and various methods and multiple perspectives are necessary. Using the urban niche can properly distinguish the levels of the relationships between urban expansion and the economic development. The relationships between urban expansion and economic development in cities with different niches present different mechanisms. The relationships between urban expansion and economic development in most high niche cities meet Kuznets curve which can be fitted with a Logistic model, and there exists a long-term balance between urban expansion and economic development. Most high niche cities are in weak decoupling state. High niche cities occupy larger spaces and more resources, having higher levels of market, so the urban expansion has a closely relation to economic development. The relationships between urban expansion and economic development in most low niche cities do not meet Kuznets curve, however that in a few cities can be fitted with a Logistic model, and the long-term balance between urban expansion and economic development is not significant. Most low niche cities are in strong decoupling state. Low niche cities occupy small spaces and less resources, having lower levels of the market, so the relationship between urban expansion and economic development are not obvious although there is certain relationship. Currently, the sizes of most cities are close to the upper limit. High niche cities should take advantage of their management and techniques to constantly improve the resource efficiency and intensive level, so as to promote sustainable economic development. Low niche cities should gradually change the binary structure of urban and rural land and adjust the industrial structure to achieve sustainable economic development.

Key words: economic development, Guangdong Province, interactive mechanism, urban expansion, urban niche