Under the shock, a traditional preload isolator can provide a good isolation performance for device.When the external shock is greater than the preload force, the force response greater than the preload force would be generated.In order to reduce the shock response of a preload isolator and improve the isolation performance of the preload isolator, a magnetic preload isolator was proposed in this paper.Firstly, the nonlinear differential equation of the magnetic preload isolator was solved by the harmonic balance method to obtain the force transmission characteristics of the system.Then, the shock response law of the magnetic preload isolator was obtained by numerical calculation.Finally, the magnetic preload isolator was compared with the shock response of the conventional preload isolator.The above calculation results show that the shock response of the magnetic preload isolator was affected by the magnetic preload and the linear stiffness; therefore, by selecting the appropriate linear stiffness, both the transmitted force response and the speed response can be significantly reduced compared to the traditional preload isolator, but the displacement response remains essentially unchanged.