Forest ecosystem, the main terrene ecosystem, plays a key role in balancing the carbon budget and keeping the water and soil in global climate change. Nujiang basin, located in Yunnan Province in southwestern China, is the main passageway and refuge for migrating species in Eurasia and is famed for its rich biodiversity. The data used in this paper is 1∶100000 scale land use and land cover maps in 1985, 1995 and 2000, which are provided by Resource and Environment Database of Chinese Academy of Science. According to natural attributes, the forest was classified to four kinds, which are forestland, shrubbery, woodland, and orchard. By using spatial intersect analysis of ARCGIS 9.0, the index of relative change degree of forest land and transition matrix of forestland change type was calculated. The researches found out: the forestland landscapes of Nujiang basin have taken great changes. The rate of forest decrease during 1995 to 2000 was much more than the rate of forest increase during 1985 to 1995, and there were 35.6% forest land which had transferred into cultivated land, glass land and construction land. Further analysis shows that the forestland change in Nujiang basin is restricted by social economy factor.