Abstract: For the large-scale tank, the max stress is near the corner (lower node) of connecting tank skin to the bottom, which is the weakest part of the whole tank. Three methods in the stress calculation for a bottom plate and edge plate of large-scale tank are contrasted. And it is found that the elastic-rigid foundation beam method is more reasonable among the methods. ANSYS software is used to do numerical simulation, and among the compared results of theoretical values, the numerical value and measured data, theory method and the finite element method are reasonable and reliable. It is concluded that the result by the finite element numerical simulation can provide a reliable validation in the design of large-scale tank, which is helpful for the designers to understand comprehensively the structural safety of tank.