Abstract: Bridge is the lifeline in earthquake relief. One of the topic objectives for aseismic design is to ensure the collapse resistant capacity of the structures subjected to a severe earthquake. A nonlinear finite elemental mode based on a long-span cable-stayed bridge is built. Firstly, the component importance of the bridge subjected to an earthquake is evaluated by using the method based on the generalized structural stiffness, in which the critical components are identified. Secondly, a progressive collapse process is simulated. Lastly, the seismic vulnerability is quantitatively evaluated based on the incremental dynamic analysis (IDA). It is shown that the collapse probability of this bridge under a severe earthquake is 0.22%, which means that this bridge has stronger ability to resist collapse during an earthquake.