The purpose of this research is to figure out the relationship between conservation of the city wall and the development of its surrounding area, by proposing what is called“city wall space”which is defined as taking the city wall and its surrounding area into account as one integrated space. The results of this study are as follows: 1) The city wall conservations law and development standard of the city wall's surrounding area are needed. 2) By the development of Nanjing city, the city wall is being changed with the urban expansion. 3) By cluster analysis which uses the data come from the function of the city wall spaces, the utilization situation and the physical features of the city wall, the city wall spaces were classified into four types, which would lead to the future planning in combination of conservation and utilization of the spaces. Finally, this paper concludes by emphasizing the new aspects of the function of city wall and the necessity of forming the city wall spaces.