Ar the first stage of a hydro-power survey of a river, it is important to select the optimal hydro-power site. The most important condition to be satisfied is to determine the optimal site where the greatest and most economical amount of hydro-energy can be obtained. This paper proposes a new method in which the optimal arrangement of the hydro-power stations is determined by a computational operation using discrete data at points along the river such as the drainage area, altitude, and distance along the river channel as obtained from topographical maps instead of drawing on engineers＇ experiences and the intuitions of experts. The results by this method are then compared with data on existing hydro-power stations and the results planned by expert engineers to show that this new computational method is superior.