Abstarct: Optimization of structures considering conditions and limitations – constraint functions – is a goal for engineers and designers. Many reasearchs done and different methods proposed yet for the solution. Generally Structures optimization in continuous environments can be classified topology optimization, shape optimization and dimensional optimization. In this investigation to solve shape optimization, we use ACOR, because ant colony optimization method is a mexta-heuristic method stablished for discrete problems. In conventional shape optimization methods that use finite elements for analysis; after each analysis in optimization, structure’s bounderies vhanges and new shape reticulates and analysis sone again; these processes is time-consuming and make problems in big problems. By emerging isogeometric methods and combining geometric and analysis , possibility of shape change ( structure bounderies ) without repetitive reticulation is provided .so in this thesis we try to use isogeometric method for analysis to change structure’s shape in optimization. In this investigation structure’s weight is the objective function and stresses’ restriction is considered as optimization problem constraint. We demonstrate the effectiveness of ant colony optimization in this thesis that is presented several examples of two-dimensional optimization problems by using a computer program.