Based on an actual project, the ABAQUS material subroutine considering damage cumulative effect and member buckling was adopted to analyze the collapse process of steel trussed arch structure. The failure mechanism and the failure mode of such structure under severe earthquake conditions were studied. The results indicated that, under the action of severe earthquakes, the cumulative damage increased and structural stiffness declined, which leading to the structure failure. The damage cumulative effect caused the decrease of the member stress and the increase of nodal displacement and member strain. Subjected to seismic waves, the webs at the columns of the middle main truss failed at first; then the failure region extended along the out-of-plane direction of the main truss and extended from the column foot to the top of structure. After the earthquake, the webs at the one-quarter point of the main truss and the webs at columns with large slenderness ratio buckled. It will lead to early failure of part members if member buckling is considered. However, it has little effect on the failure mode of structure.