Impervious surface expansion has a prominent impact on the process, function and service of urban ecosystem, so exploring its variation is of great significance to urban development. Based on the land use data from 2000 to 2020 in Nanjing, we integrated landscape spatial gradient analysis and pattern analysis method, setting radial gradient zones around the downtown by expanding outward at equal distances to analyze the spatial and temporal distribution and gradient characteristics of impervious surface. Meanwhile, the transects along and across the Yangtze River were set to analyze the driving forces behind the expansion scale and direction variation of impervious surface. It could provide policy suggestions for the landscape pattern optimization of Nanjing. Results showed that: (1) Impervious surface landscape dominance showed a downward trend along the gradient zone. The urban center was highly concentrated with well-shaped impervious surface. The peripheral urban area was the key regions of impervious surface expansion, accompanied with the reduction of arable land, forest land, water body and other natural landscape, so the landscape pattern of this area changed drastically. The suburban area impervious surface maintained slow and steady expansion. (2) Topography and river system significantly affected the expansion direction of impervious surface, planning policy would play a certain regulatory role. Economic development, population growth and industrial structure adjustment and optimization affected the expansion scale of impervious surface. (3) Nanjing should optimize the urban landscape pattern from three aspects improving the urban living space, transforming the mode of urban development and controlling the urban expansion.