Several vibration-isolating equipments with metal spring, air spring, rubber spring, a shock absorber and a viscoelastic damper are developed by aiming at the optimum adjustments. The purpose of this paper is to study the new spring-mass system using non-linearity of magneto-spring and instability of float control. The dynamic spring constant and the damping coefficient of magneto-spring are dependent of a motion of amplitude. They are a much better characteristic for the suspension system compared with the current mechanical pairs composed of metal or air spring and a shock absorber. The vibration-isolating structure that combines the non-linear magneto-spring and the linear metal spring has the same effectiveness as a dynamic vibration reducer. For that reason, the suspension system using magneto-spring can reduce the vibration energy with a small stroke.