Abstract: The research on the characteristics and dynamic mechanism of the construction land use growth in the small and medium-sized cities is the breakthrough point of city’s management and control of high quality in the new era from the geographical zone perspective in Northwest China. It is also the key to promote a new pattern of coordinated development in the corresponding regions. Based on the interpretation of the remotely sensed images and large scale supplementary data of the small and medium-sized cities in Northwest China over the past 15 years, the time discreteness, the spatial difference and the aggregation extent of the growth were analyzed using the method of annual growth rate, centroid migration rate, topological relation and fractal dimension to measure the rate, direction, pattern and boundary shape of the urban construction land use growth. Then, the study investigated the growth motivations and summarized as follows: the implantation of key industry or main function promotes the urban extrorse growth with medium or high-speed epitaxial growth; the disturbance of land ownership in urban fringes leads to a directionless irregular growth with low speed and yet this irregularity was gradually forced to become regularized by the slow and well-organized construction in the fringes; the fill-up type of development of the land use between urban districts impels this padding alike type of growth with low-speed and weak-direction. Based on the findings, this paper puts forward the classification and guidance strategies for the cities with different growth driving forces in their future urban land use planning and control decisions.

Key words: small and medium-sized cities in Northwest China, urban growth, spatial-temporal characteristics, motivation analysis