Abstract:

On the basis of understanding the connotation of the spatial structure and defining the scope of research，applying the principal component and cluster analysis methods，the spatial division of the Yangtze River basin has been attained．The spatial structure of the Yangtze River basin，which conforms to the mode of the coreedge structure，includes three firstorder cores，eight secondorder cores，two big transprovincial growth triangles，one main axis，two secondary axes，three locational axes，one peripherical region and one edge region．The spatial structure of the Yangtze River basin was formed after the lowlevel dispersal period，the polarization developing uneven period，and the diffused multicore uneven period，and will enter the regionintegration highlevel even period in the future．From three aspects of the assembly and diffusion theory，the spatial interaction and the national macroregional developing strategy，the evolution mechanism of the spatial structure of the Yangtze River basin has been analyzed．To optimize the spatial structure of the Yangtze River basin，we should start with the internal factors and the external force．Firstly，we should speed up the development of individual node and the formation of core region，especially in upper reaches region we should build up a growth polygon that has two cores of Chengdu and Chongqing and includes a big scope from south to north．Secondly，we should quicken the construction of eastwest passageways and the buildup or the perfection of passageways between main axis and secondary axis．Thirdly，we should bring forth new ideas in the regional spatial administrative system based on the market integration.

Key words: the Yangtze River basin/the shape of spatial structure/ evolution period/evolution mechanism/ the optimization of spatial structure