Abstract: The spatial morphology of out area of a city is the exterior exhibition of its spatial organization. The rational spatial morphology is valuable for the development of urban elements and resources. There is an inherent evolutional rule for the fractal dimension of spatial morphology in different temporal sizes, and there is a linear relationship between the fractal dimensions and the population, and also the area. Taking Wuhan as an example, the outer spatial dimensions, populations and areas are calculated, and there is a consanguineous functional relationship between urban size and the outer morphological fractal dimension. The describing morphological function can be constructed based on abovementioned research. It is considered that the fractal dimension can be regarded as the indicator to forecast the urban spatial expansion and evolvement, and the developing mechanism of urban spatial morphology can be analyzed using the correlation between the fractal dimension and social and economical factors.

Key words: spatial morphology, fractal characteristic, evolutive rule, Wuhan City