Abstract: A nonlinear dynamic model for the isolation system of steel-wire isolators is constructed with the introduction of a softened frequency coefficient based on static mechanical properties for steel-wire isolators. The dynamic responses to impulse and random vibrations of this system are investigated with the nonlinear dynamic model. The simulated results are discussed. The theoretical analyses and simulated results show that the nonlinear dynamic model with the softened frequency coefficient has a better isolation effect compared to the linear Hookean spring model.