Abstarct: Concepts discussed in the thesis is given as, in three parts of acquaintance of Arch dam and their methods of Design and Analysis, introduction of Isogeometric Analysis and shape optimization with this method. At the end Double-arch dam in three preliminary design stages, Isogeometric Analysis and optimization of shape, with this method presented step by step and was assessed with same numerical examples. Arch dam is generally a concrete construction that has a curvature and arch towards upstream and transfers the created loads by water to supports sides of it and sides of valley and facilitates the most beneficial usage of materials compressive strength. Although dams arch itself somehow optimizes dam’s shape, but design and Analysis of dams are done with trial and error method to achieve an acceptable design with common Analysis, specially Finite Element Method, doesn’t result in optimized design necessarily, therefore shape optimization of is so important. Usage of Finite Element Method, specially in analysis of arch dams, has sufficient accuracy when is used of three-dimensional elements with proper amount for three-dimensional solution of dam. On the other hand, due to body’s curvature, for adaption of networked model with actual geometry of dam, it needs to decrease dimensions of elements and increase quantity of them. This issue at the time of using three-dimensional elements, due to increase of quantity of non-linear equation, have much problems and it needs high volume of computer memory and much time. In Isogeometric Analysis , definition of geometry is done with high accuracy. In addition , change of boundary surfaces during optimization doesn’t make a dent in uniformity and smoothness , in addition , advantage of this method is remove of construction phase of finite element network, during optimization. this action has caused significant decrease of calculations , specially in three-dimensional questions ,for example double-arch dam. Meanwhile , due to flexibility of NURBS in Isogeometirc method, boundaries changes doesn’t cause loss of stability of solution. Therefore , in general , it can be concluded this method is assessed cheaper and more accurate than common methods.