Abstract: This article caculated the direct solar radiation value based on the simulation model of the sun direct radiation of ViewGIS. Also,fixed-point measured data are set,a benchmark and the model are tested precisely. The research applies space distribution rule and features for the area sun direct radiation so as to provide basic support and scientific basis in the local ecological environment construction and agricultural production distribution.The results show that the total amount of sun direct radiation per day presents features that the south less while the north more in Yanchi county; the sun direct radiation amount decreases with the increase of slope gradually. The total amount of sun direct radiation per day decreases with the slope as follows:sunny slope,semi-sunny slope,semi-cloudy slope,cloudy slope.Forestry ecological construction should make full use of solar radiation law,in northern gentle slope hills area combined with fencing grazing grassland productivity and maintenance of grassland biodiversity; in the Southern Loess Plateau area,full use of direct solar radiation shall be made and water-saving economic forest and fuel forest devloped.

Key words: direct sodar radiation, spatial distribution regularities, Yanchi County