We divide the whole Yangtze River Delta into many square cells. The area of every cell can be defined arbitrarily. In this paper, we define area of one cell as 500 m500 m. The whole region can be divided into 399,192 effective cells. Thus the cells number of each city can be gained (Table 1). One cell of 0.25 km2 is very small compared with the Yangtze River Delta whose area is 10.9104 km2. Accessibility is almost no difference within such a cell. There- fore, we regard cells as points whose accessibilities are homogeneous in the region.