The loss of water and soil is the most serious problem in Loess Plateau region of China. The shelter forest system project has been performed in Loess Plateau region from 1978 to improve the ecological environment. With the method of knowledge-based expert system, this paper classifies the Remote Sensing image of 1980s、1990s、2000s and 2007s. From the acquired land-use map, we can abstract the distribution map of the shelter forest land, which aims to monitor the shelter forest in Loess Plateau region. The m...