Abstract:  

To explore urban core built-up area’s influence on construction land growth, newly-increased construction patches from 10km buffer of core built-up area in 77 cities above county level of the Yangtze River Delta were selected as the research object. Characteristics and expansion mode of newly-increased construction land were analyzed through expansion intensity , landscape metrics index and spatial analysis methods. The results showed that:Firstly, from 1990 to 2015, each grade city’ s average area of newly-increased construction land fluctuated in cycle riseand had close relationship with plan of Country or local goverment. Meanwhile, the higher the city grade, the larger the extension scale. Secondly, with the distance increase from core built-up area, expansion intensity of patch samples in each grade city had an overall declining trend andlandscape isolation was on the rise as a whole. Extension intensity kept a decline logarithmic curve relationship with distance from core built-up area. Thirdly, in the research period,there were two obvious stage characteristics of urban expansion mode: Urbanization stage was from 1990 to 2000.the growth of construction land gathered by mainly centripetal infilling type .Suburbanization stage was from 2000 to 2015.The growth of construction land mainly diffused by centrifugal edge-expansion type in spheres structure. Outlying expansion type of large and small cities enhanced significantly. Medium-sized cities maintained a high growth rate by edge-expansion sprawl type. In view of different grade and stage of city development, policy guidance and government planning has important effect to reasonable layout of the land.