The System Analysis of Force about Factor Impacting on City Size - The Case of Changshu City in Jiangsu Province

The reasonable value of city size is required in the process of city planning with the rapidly development of urbanization. The paper divides some factors impacting on city size into three strikes of sustaining, restricting and driving, with the help of strike definition in physics. When three strikes are on balance, city development is considered among reasonable scale. Firstly, based on revised eco-footprints method, sustaining strike is applied with land area to response the sustain ability of city development. Secondly, applying the method and theory of thresh analysis, restricting strike is included energy, water resource, land resource and environmental capacity, and analyzing them restricting city development. Thirdly, driving strike mostly is analyzed by the use of semi-quantitative method. At the same time, Changshu city in Jiangsu province is system analyzed as the case using the above corresponding method and theory. It is concluded that it has only 50% land area to sustain itself and it is a typical export city. And it´s restricted strikes include water resource and environmental capacity.