Abstract:Human activities, resulted in land use and land cover changes, are main causes of global environmental changes. In 1990s, Yunnan had experienced very active economic development and environmental changes. This paper assessed the land use and land cover change between 1990 and 1998 in Lancang watershed by applying remote sensing, Geographic Information System(GIS) and other disciplines.It showed that the state designated forestland had increased from 64.9% in 1990 to 66.4% in 1998, however forest cover (natural forest and artificial forest with closed canopy >30%) had decreased from 52.6% in 1990 to 35.3% due to large-scale logging, infrastructure development, cash crop plantation, shifting cultivation and over-collection of fuelwood and construction material, which resulted in change of forest structure and loss of biodiversity.