Abstract: The elastic-plastic analysis of a long-span Concrete Filled Steel-Tube (CFST) transmission tower under earthquake actions is studied by the static method and the dynamic method, including: 1) fine FEM models of a CFST tower and a tower-line system are built and the nonlinear material models including steel-tube and CFST are also modeled. 2) shear forces on supports obtained by a mode-decomposition response spectrum method are distributed at all nodes based on the structural first-order mode value and then the nodal loads increase step by step in order to impel materials into plastic status until calculation cannot converge. Static analysis shows there are some steel-tube elements failed but no any CFST element failed and the limit load is decided by the steel-tube elements. 3) a seismic record is selected to analyze the seismic elastic-plastic behaviors of the tower by a time-history analysis method. The dynamic analysis shows a lot of elements enter the plastic status soon after earthquake action and there are some steel-tube elements failed but no any CFST element failed at last time, so the tower can achieve the goal: no collapse in the big earthquake. The two methods both show the weakest part is in the middle of the tower.