The diploma thesis deals with design of steel tanks. Since the steel tanks are very slender (high ratio between the radius and plate thickness), special attention should be given to stability check. The most critical load situation to stability loss is when the wind load acts on the empty tank. To increase the buckling resistance of the steel tank the ring stiffeners are applied. Within the framework of the thesis the international design specification for buckling design of ring stiffened steel tanks (API650 and EN 14015 Standard and European recommendations ECCS 5th Edition) are given and compered. The design recommendations were used and compered on the already-built tank, for the built and current state, where the plates thicknesses were reduced due to steel corrosion. Additionally the LBA, GMNA and GMNIA numerical analysis of the tank were performed and compared to the results obtained by the design specifications. The GMINA analysis was used to compare numerically obtained resistance to design specifications, while the LBA analysis was used to find the optimal position of the ring stiffener and to reproduce initial imperfection shape for GMNIA analysis. One of the main ideas of the diploma thesis was to build a computer program that would perform stability design of ring stiffened tanks. To this end the program “BuckleTank”, which allows for buckling design of new as well as existing tanks in accordance to above mentioned design specifications was build. In addition the program also allows the generation and execution of python file which performs required analysis (FEA, GMNA, GMNIA) in program SIMULIA Abaqus FEA.