Abstract: At present there is no design standard in designing large steel SCR (selective catalytic reduction) reactors. According to numerical analysis on the structure of a steel SCR reactor, the stress and deformation as well as weak position of whole construction are obtained. The results derived from geometric linear analysis and geometric nonlinear analysis are compared. According to the results, the data based on geometric linear analysis are conservative, and the stress distribution is more homogeneous when large deformation is considered. It turns out that the rational design of the reactor structure has a surplus to meet the needs of safety and the use function of the reactor.