Abstract: Collapse safety is the most important objective of performance-based aseismic design. Buildings should have an enough safety margin to avoid collapse subjected to a severe or mega earthquake. However, current Chinese seismic design code for building structures does not provide an explicit design or a quantitative evaluation method for collapse-resistant capacity. In this paper, the collapse-resistant capacities and safety margins against collapse of multi-story reinforced concrete (RC) frames with different seismic fortification levels are quantitatively evaluated, with a collapse fragility analysis based on an incremental dynamic analysis (IDA). The influences of the axial compression ratio and the failure mode to the collapse-resistant capacity are discussed, and suggestions are proposed to improve the current design.