The steel structure of large-scale electric dust precipitator applies the combination structural system of spatial bars and shells,which has various bar and complex bearing states.It is not appropriate for the traditional calculation method to precisely evaluate the bearing capacity of the structural system,so a further nonlinear analysis is needed,and the structural system and member section need to be optimized.A finite element model of the vertical beam(only under moment,under both larger axial force and moment) of steel shell structure is established for a large-scale electric dust precipitator with finite element software ANSYS.The static analysis of the integral structure,eigen buckling analysis and ultimate strength analysis are proceeded.Based on the results of the analysis,this paper proposes an optimized program for the vertical beam only under moment.The calculation results show that the two types of beam model are designed to meet the loading capacity requirements.