Based on the TM images of 1985 and 2000, the paper analyzes changes in land use of the Minjiang Watershed and reciprocal transformation of land use between types quantitatively with the aid of GIS. Spatial differences in the changes of land use and their driving forces between two counties, Jianyang and Changle, were also discussed. The results showed that the increasing population, industrialization, urbanization and macro-policies of the government were the main factors that caused increase in farmland, woodland and built-up land and decrease in grassland and virgin land during the past 15 years.