Research on Agglomerative Effect of City Group under Regional Coordinated Development

City group is one of the core strategies in regional development, the inevitable choice under the special national conditions, the critical support of regional coordinated development, and also the leading force of urbanization. This paper compared the present situation of three typical city groups in China and measured their combined effect. Then it gave these conclusions: first, there is significant positive combined effect in all of them. The effect of Wu Han city group and Chuan Yu city group is much larger than it in Chang San Jiao city group. Second, the change of relative size of effect is coordinated with the change of regional gap in economic development. Third, regional Coordinated development lays on for one thing the industry transfer, for another the establishment of particular dominant structure of industry.