Abstract: Urban function has always been one of the hot-spot subjects having attracted the attention of domestic and overseas geographical circles. China has mainly followed the steps of western countries in researching the issue of urban function, but has seldom made original explorations. In addition, China's researches on urban function are unnecessarily confined to the classification of the functions and lack overall measurement of regional urban function systems and their complementation. In recent years, along with the emergence of integrated regions, the research on the urban functions of the regions with high integration degree such as the Yangtze River Delta has become a hot topic. With the Yangtze River Delta as research object, 139 districts and counties in the region as basic spatial units, based on the 10% sampling survey data among the national census data in 2000 and 2010, this paper has extracted the information on industrial workforce population divided by "industrial type" of each district and county, consolidated and reduced them into seven functional types, and analyzed the internal functional division and spatial clustering characteristics of the Yangtze River Delta from two lateral layers, namely, structure attribute and space attribute. This paper first measured the scale differentiation and spatial clustering degree of each function in the region by means of Lorenz curve and Ellison-Glaeser index(EG), and then analyzed the spatial clustering of functions in each district and county with functional location entropy as basic data, and surveyed the spatial distribution and change of each function clustering district. The research shows that, as seen at national level, in the Yangtze River Delta, "commerce and trade" and "industry" are generally the main functions, showing the trend of being further strengthened, while agricultural function is being weakened continuously. The internal functional division structure in the Yangtze River Delta shows the trend of constant professionalization, and professionalized service functions like "commerce and trade", "modern logistics", and "education and scientific research", etc., are gradually centralized in the core areas of three central cities, Shanghai, Nanjing and Hangzhou, while the districts clustered with "industry" function are distributed in Shanghai-Nanjing axle areas, and are gradually transferred and spread to the areas along the Yangtze River and the coastal areas of Hangzhou Bay. Along with the deepening of regional integration development, the functions born by individual units in the Yangtze River Delta are being gradually transformed in professionalized direction, and also, the same functions have gradually clustered in similar spatial location, forming a spatial clustering district featured by some professional function. The professional service functions such as regional business, commerce and trade, logistics, education, and scientific research, etc., will be increasingly centralized in central cities, and it's easy to form a manufacturing clustering district in the areas close to central cities. Generally speaking, the areas having stronger relationship with central city Shanghai in the Yangtze River Delta have higher degree of functional professionalization. With the scales of workforces in different industries, as shown in the previous two census of population, as preliminary data, this paper can approximately reflect the pattern of functional division in internal regions of the Yangtze River Delta, but meanwhile, it has certain deficiencies. For example, it neglects the differences among labor-intensive and technique- and capital-intensive industries in terms of employment rate and labor productivity, etc. These deficiencies need to be corrected in the future research by subdividing industrial categories, introducing economic data, and so on.

Key words: county level, function clustering district, the Yangtze River Delta, urban function, workforce population