: This thesis gets through determination of optimum values of design variables related to a domed structure under gravitational and lateral loadings. Above mentioned structure consists of a spherical dome relying on a ring beam that has settled on a cylindrical wall. To achieve above purpose, a program has been written using mathematica programming language that contains analysis, design and optimization subprograms of structure. In this program, principles and relations of fundamental theory of shells have been used to analyze structure by assuming of initial values for design variables such as members dimensions and bars number and stirrups spacing. Then using results of analysis of structure and considering design rules of Iranian concrete code, total cost of structure consisting of concreting and bar bending and formwork costs was minimized as a function of design variables. Using optimum values of design variables, these were obtained after optimizing, above stages again repeat and this repetition continues until cost minimum value of project in current repetition equals to that in previous repetition with an appropriate precision. Result of this thesis is a program named RECDO that analyzes an more usable domed structure by effective methods and finally gives an optimum design with complete details and thus considerably saves in total cost of project in addition to increase precision, ease and design speed. For parametric studying, above mentioned dommed structure has been analyzed, designed and optimized by RECDO program in 16 various cases with 4 different values for each of parameters of dome span, dome angle, wall height, compressive strength of concrete and yield stress of steel.