Abstract: To study the effect of seismic grades on the seismic collapse-resistant capacity of reinforced concrete (RC) frame structures, 20 typical RC frame structures were designed with different seismic fortification levels and different seismic grades according to the Chinese Seismic Design Code (GB 50011-2010). Collapse fragility of RC frame structures was analyzed by the incremental dynamic analysis. The seismic collapse-resistant capacities of RC frame structures with different seismic grades were compared. The result showed that seismic grades had an important influence on the seismic collapse-resistance capacity of RC frame structures. At the same seismic fortification level, the collapse probability decreased and the collapse margin ratio (CMR) increased with increasing seismic grades. The seismic collapse-resistance capacity of RC frame structures improved with increasing seismic grades. The axial compression ratio, longitudinal reinforcement ratio and the volume stirrup ratio of frame columns were important factors affecting the seismic collapse-resistant capacity of RC frame structures.