Since the late of 1990s the urban space has increased fast in the Yangtze River Delta due to both the central city′s extension outward and urbanization in the suburban of metropolitan areas. The rapid urban expansion has changed land use/cover, while a lot of land use policies of nature conservation have also been implemented to diminish the ecological environmental effects of changes. For these two opposite processes the ecological space performing high ecosystem services function has complicatedly varied. The variation should be theoretically investigated with emphasis on human factors. Based on the land use data interpreted from TM images of Nanjing in 1986, 1996 and 2002, in this paper we first analyzed the changes of area and quality of ecological spaces during the rapid urbanization since the open policy, then probed into the driving forces in aspects of economic development, national policies and urban expansion patterns. Furthermore, after exploring the spatial temporal evolution and the change models, we finally gave some policy suggestions for ecological space protection. Several points could be drawn from the investigations: (1) In the period from 1986 to 2002 the green space increased and the blue space decreased, while in general the total area of ecological spaces maintained stable; (2) The ecological spaces′ ecosystem services value decreased and the landscape tended to be fragmented into artificially regular patches; (3) The composition of ecological spaces varied in different urban zones. In the main city, as the direct frontier of urban expansion, the quantity and quality of ecological spaces decreased quickly in 1986-2002. In the near suburban zone as the urban-rural interface, the water area and wetland with much high ecosystem services value were invaded or even occupied by urban spaces and agricultural land, thus the quality of ecological spaces decreased even though the total area of ecological spaces increased a bit due to series of national policies as returning arable land to forest, adjusting agricultural structure and etc. Therefore a conclusion emerged that the effect of area-control policy was limited on conservation of ecological spaces. To what extent it took effect relied on a series of governmental intervention and adjustment activities on urban growth and natural conservation. The research results may provide scientific basis of the policies of ecological space protection, and enrich the safe and healthy urban ecosystem study based on land use/cover change.