Urbanization is a newly emerged problem in developing countries worldwide in nowadays. It has caused many ecological and environmental problems, which make it necessary to describe the process of urbanization to deal with these problems. Beijing, the capital city of China, also experienced a rapid urbanization in the past two decades since the reform and opening up policy launched by the central government in 1980's. Based on the remotely sensed data of Beijing at the years of 1984, 1991, 1994, 1997, 1999, and 2002, GIS and Fragstats analysis showed that the landscape metrics indicated a fragmentation of the city during the process of urbanization at both landscape and urban type levels. Transect sampling on the images and urbanization rate analysis showed that the Beijing expansion was different in directions in the past 18 years, which can be described as a West-East direction enlargement in 1980's, a North-South direction enlargement in 1990's, and a Northeastern and Southeastern enlargement in 2000's. The main driving forces of the urban sprawl were population and economy booming and the resulting infrastructural and housing construction, environmental protection policy, and the limitation of regional topography. The case of Beijing gives an example of urbanization study to other developing countries, and will be beneficial to a better understanding on the mechanisms of urbanization quantitatively.