Abstarct: This thesis consist of some theoretic studies in order to use ant colony optimization algorithm to design tailraces. The algorithm has been written and run by visual basic program. Aco is one of the modern technics that has been attentioned by researchers recently. Aco plan process with discrete variables consist of open form to assign constrains and various analyses. Also utilization of saxo turbines has increased recently. That is because of their ability to generate electricity without larg reservoir in approach flow that may causes to environmental pollution. Use ant colony in order to optimizing tailraces is the last purpose in this thesis. So objective function has been considered with design variables such as ground slope at the different parts, contraction and expansion intensity. Finally it assume that by simulating the acts baxsed on swarm intelligent with computers to optimizing the solution.