Abstract: The space-time characteristics of urban expansion and its driving factors help understand the laws of urbanization and provide a scheme for the formulation of urban spatial planning with regional characteristics. This study was a case of Nanchang City, where Multi-source data from Landsat (in 2000, 2008 and 2017) were used to obtain the space-time information of urban expansion and were analyzed using the expansion intensity index, landscape expansion index and center of gravity index. The influencing factors were then analyzed using the boosted regression tree model (BRT). The results show that：(1) From 2000-2017, the urban expansion area in Nanchang increased by 252.81 km². The intensity and speed of growth was comparatively greater during the first phase (2000-2008) than the second phase（2008-2017）. (2) In both the phases, the urban expansion pattern was dominated by edge expansion, some of them supplemented by infilling and outlying expansion, which was random and less intensive. (3) In the period of 2000-2017, the center of the city moved 2.19 km to the southwest. The shift in the first phase was 1.5 km west and 1.35 km southwest in the second phase. (4) Among the 16 directions, SW and SWW had comparatively larger urban expansion with NW, N, NNE, SE, and SSE directions expanding much smaller due to the natural barriers of the Meiling Mountains and the Junshan lakes. (5) BRT analysis of the neighborhood factors (distance from the city in 2000, rivers and road network), social factors (land use type, GDP and urban population) and natural factors (elevation, slope and aspect) showed that the urban expansion of Nanchang City has been mainly affected by the neighborhood factors. And among the social factors, only land-use types have a greater impact on urban expansion, while the influence of natural factors is relatively weak.
Key words：urban expansion; boosted regression tree; driving factor; Nanchang city