South Korean self support rate for the grain product is less than 25oyo, and depends on the imported product for the national food supply. Therefore, there is imminent need for development of agricultural decision support system using GIS which provides various useful informations for a more accurate agricultural policy making. Agricultural decision making processes are complex due to complicated current international political situations, and the erratic weather condition like that Elnino, flood and drought etc. Hence, global scale GIS and analytical applications has implemented for solving the agricultural problems above mentioned in this study. As the results, the executable decision process with GIS developed well adopted for the rice cultivable area estimation in the world.