Abstract: The city is a complex giant self-organizing system,and it is also an other-organization system which is influenced by human intervention through its growth.Both the self-organization part and the other-organization part have left a deep mark on the resource-based cities and under their combined effects,how to understand scientifically the law of the urban spatial change can help set up the strategy to promote the transformation and development of those cities.Taking Baiyin City,Gansu Province,China as an example,this paper selected its construction land information in 1953,1986,2000 and 2016 as the data source,and quantitatively analyzed its urban spatial evolution using GIS technology.The results revealed as follows:(1) the urban spatial evolution had experienced three stages with the first stage being its growing-up stage (1953-1986) dominated by other-organization mechanism,the second stage,the stage of the fluctuations in its development (1986-2000) influenced jointly by self-organization and other-organization mechanism and the third,the transformation development stage (2000-2016) dominated by self-organization mechanism.The three stages indicated that not only the self-organization mechanism played a great role in the process of urban spatial expansion,but also the other-organization mechanism provided indispensable guidance and management throughout the evolution. (2) the intensity of urban spatial expansion is increased in general from the longitudinal time perspective with the obvious differences among the different types of urban construction lands.From the horizontal space point of view, each stage had its own dominant expansion direction and scope.All of these showed that the intensity and scope of urban spatial expansion under the self-organization mechanism or other-organization mechanism had been changing along with the changes in the national economic system,urban economic transition and urban spatial structure. (3) There were irrational construction land structures over the course which was reflected by the fact that the industrial land had a larger proportion and exceeded the national standard.Although it is shown as one of the characteristics of the resource-based cities,it exceeded significantly the national standard not only for the individual residential land per capita and industrial land per capita,but also for the construction land per capita. (4) The relative growth relation between the urban space and the city's population and economy was tending to become good.The space compactness was increased as the dispersion degree and fractal dimension of urban spatial form became decreased.All these indicated that the evolution of urban spatial expansion is an optimization process which can make their respective advantages complementary to each other for both self-organization mechanism and other-organization mechanism.

Key words: urban spatial expansion, self-organization, other-organization, Baiyin City