Inherent twinnability of face-centered-cubic(fcc) metals was analyzed based on the direct competition between twinning partial dislocation nucleation and trailing partial dislocation nucleation,with which the twinnability of fcc metals can be simply expressed as function of the stacking-fault energy,the unstable stacking-fault energy,and the unstable twinningfault energy of fcc metals.The predicted twinnability ranking matched well with former experimental results and provided a physical insight to understand twinnability from crystallographic orientation and fault energy parameters. Inherent twinnability of face-centered-cubic (fcc) metals was analyzed based on the direct competition between twinning partial dislocation nucleation and trailing partial dislocation nucleation, with the twinness of fcc metals can be simply expressed as function of the stacking-fault energy, the unstable stacking-fault energy, and the unstable twinningfault energy of fcc metals.The predicted twinnability rating matched well with former experimental results and provided a physical insight to understand twinnability from crystallographic orientation and fault energy parameters.