Interpolation, the generalization of point data to scatter data, and combining maps are three cases of important applications of GIS. In this study, it has been tried to make the estimation of rain erosion capacity (Fournier Method) more real through using GIS capability in interpolation and the generalization of point data to scatter data. In Fournier method, the rain erosion capacity is calculated through the use of two climatic parameters (annual precipitation and the rainfall mean in the rainiest month of year) and two physiological parameters (the height and slop of the region). The findings of this study indicated that there is significant difference between these two methods of calculating rain erosion capacity. Using the means of rain erosion potential was estimated to be almost 3.4 tones per square kilometers annually while this amount was estimated to be 4.5 tones per square kilometers annually by using GIS capabilities. [Amir Gandomkar, Estimating the Real Capacity of Rain Erosion Using GIS (The Fournier Case Study for Isfahan). International Journal of Agricultural Science, Research and Technology, 2011; 1(1):33-38].