The ideal failure mode of building structures is the full beam-hinge mode. However, in the actual earthquakes, the beam-hinge failure mode is unpredictable due to the existence of various uncertainties. The story failure mode, local beam and column failure modes can be transformed to the global deformation and full beam-hinge failure mode with the function of rocking truss. The random incremental dynamic analysis (IDA) was used to identify the probabilistic earthquake failure modes of steel frame, steel frame with rocking truss. Then the probabilistic seismic collapse capacities of structures were compared through the collapse fragility. Thus the optimization and control of failure modes of steel frames will be achieved with rocking truss, and the structural seismic performance and collapse capacity of steel frames can be significantly improved with adoption of the proposed rocking truss.