It is important for the urban agglomeration of the Changjiang(Yangtze) River Delta to the regional development in China.In order to find out the characters of spatial changes of the Changjiang River Delta and give the guidance for the future development of this area,this paper firstly defines the urban agglomeration gravity,then calculates and analyzes the urban agglomeration gravity of the Changjiang River Delta and its changes from 1994 to 2004,according to the method of regional population gravity.Furthermore,based on the above analysis,the paper explores the driving forces of the urban agglomeration gravity changes in the Changjiang River Delta from three aspects,such as natural and spatial characters,economic development,social conditions and so on.The result shows that the urban agglomeration gravity has been moving more than 20 km to the northwest of the Changjiang River Delta since 1994,and the location of gravity moves from the boundary between Suzhou City and Jiaxing City to the vicinity of the center of Suzhou City.Moreover,the urban agglomeration gravity will still move toward northwest and locate at the boundary between Suzhou City and Wuxi City in the near future,from the direction of former changes of the urban agglomeration gravity in the Changjiang River Delta.In detail,all these changes mainly attribute to the following three aspects:First,the natural and regional conditions of the northwest cities in the Changjiang River Delta are better than those of the southen cities.Moreover,along with the rapid development of transportation,the northwest cities will be more important in the urban agglomeration of the Changjiang River Delta,and drive the urban agglomeration gravity to the northwest area of the Changjiang River Delta. Second,there are significant differences of economic development among cities in the Changjiang River Delta.From the values of main development indexes,such as GDP,structure of industry,investment in fixed assets,and place in urban development competition in China,it is clear that the northwest cities in Jiangsu Province develop with greater speed and have a higher position than the southen cities in Zhejiang Province of the Changjiang River Delta.Therefore,the economic development difference among cities in the Changjiang River Delta is considered one of the main forces driving the urban agglomeration gravity changes in the Changjiang River Delta. Third,as for the social conditions(including social development and environmental condition),they also have important effects on the movement of the urban agglomeration gravity in the Changjiang River Delta.During the past ten years,most of the social conditions of the northwest cities in Jiangsu Province were better than those of the south cities in Zhejiang Province,such as environmental quality,culture and educational development.As a result,the northwest cities develop with greater speed and larger size than the south cities and promote the urban agglomeration gravity to move toward northwest. In the end,some conclusions and suggestions are stated.The author emphasizes that it is necessary to give prominence to Suzhou City and Wuxi City and strengthen the relationship between these two cities and others of the Changjiang River Delta in the further development.