Urbanization and industrialization have been developing rapidly since the enforce-ment of the reform and the opening-up policy.Consequently,the built-up area keeps expanding,and it gradually becomes a threat to national food security.Based on the literature review,researches on built-up area expansion of city and town using RS and GIS have become a hot pot in Geography in recent years.However,most of them focus on developed area and plain area,such as Yangtze Delta,Zhujiang River Delta and Bohai Rim,but pay little attention to hilly area.This study selects Tonglu County as a representative case in which about 79% of land is mountain,9% is farmland and 12% is water area.Supervised classification combined with spectral signature analysis is used to extract town land information in Tonglu County from serials of Landsat images acquired in six different years(1978-2002).Next,the town land information and land use data are used to measure the area and intensity of built-up area expansion,spatial pattern and morphology of towns in Tonglu County.Based on which,the characteristics of town land expansion in hilly area of western Zhejiang province are identified.The driving force of town land expansion is stated with different views of aspects,such as physical condition,social-economy,transportation,etc.The result indicates four phenomena as following:①Town land expansion is shown in three obvious phases:low expansion in the 1980s,speeding up expansion in the 1990s and rapid expansion after 1999.And the year 1999 is the milestone at which towns began to expand rapidly.Central district entered this stage prior to other towns,and most ordinary towns haven't been in this stage.②General spatial frame of towns presents a "T shaped" pattern,and it became more and more salient.Fuchun River and Fenshui River are two development axes of it.Central district is located in the center of the "T shaped"pattern,and Fenshui Town is its western center.③"Axes Mode" and "Skip Mode" are the underlying modes of built-up area expansion.As a result,spatial morphology of towns becomes more and more complex.④Built-up area expansion is influenced by many factors.The hilly area of terrain determines general pattern of towns.Growth of economy is the internal driving force of built-up area expansion.Adjustment of regionalism,town planning and policy have instructional influence on town land expansion.And the improvement of transportation speeds up town land expansion.