Closing land for forest or grass is a important project, which was developed in west-China in 2000, in improving environment, water and soil preservin g and reducing natural disaster. Minjiang river is an important branch of Yangt ze river. Its water and soil preserving will affect environment of Yangtze river drainage directly. The essence of closing land for forest or grass lies in wate r and soil preserving. Remote sensing and geography information system (GIS) tec hniques were applied to extract the sloping land information and describe all fa ctors of the USLE model. The universal soil loss equation (USLE) is used to calc ulate the annual soil loss, and characterize the spatial distribution of the ris k of soil erosion by water in Minjiang river drainage. The relationship between sloping land and soil erosion will be analyzed, which is in different slope for determining the criterion of closing land for forest or grass. In the end, the change of environment and soil loss is evaluated before and after closing land for forest or grass in Minjiang drainage.