By using 1985, 1995, 1997, 2000 and 2004 satellite images and GIS technology, three indices including built-up area density, expansion intensity index, and fractal dimension were chosen to analyze the spatiotemporal characteristics, spatial differentiation, and morphological changes of urban and rural built-up areas in Shenyang City in 1985-2004, with the main driving factors discussed. In the study period, the high-density area of urban built-up area in the City increased year by year, and that of rural built-up area changed slightly before 1997 but increased gradually thereafter. The increased area, expansion speed, and expansion intensity of built-up area were evidently greater in urban than in rural area. An obvious spatial differentiation was observed in the expansion of built-up area between urban and rural areas, with the high-speed expansion mainly concentrated in urban area. The fractal dimension in urban area increased gradually, which meant that the integrated configuration of urban area became more and more complex, while that in rural area changed irregularly, because of the lack of reasonable planning and construction. Economic development, population growth, transportation, natural environment, policy-guiding, and urban planning were the main driving forces of the expansion of built-up areas in Shenyang City.