In view of the contradiction that the traditional linear vibration isolator will sacrifice the vibration isolation performance while reducing the resonance peak, a vibration isolator with piecewise damping is designed. First of all, the variable damping device of moving cam is used. With the design of cam profile, the vertical damping coefficient of the system is controlled by the magnitude of vibration displacement and presents piecewise linear characteristics, and the damping characteristics of the device are analyzed. Then the piecewise damping device is applied to the vibration isolator, and the active vibration isolation system model with piecewise damping and its dynamic equation are established. The equivalent linear damping coefficient of the piecewise damping system is obtained through the energy equivalence principle, and the theoretical solution of the system response under simple harmonic force excitation is solved. The correctness of the theoretical solution is verified by the numerical simulation of the fourth-order Runge-Kutta method. Finally, the dynamic characteristics of the piecewise damping vibration isolation system are studied, and the effects of the main parameters on the amplitude frequency response characteristics and force transmissibility characteristics are analyzed. The results show that through reasonable parameter selection, the piecewise damping vibration isolator can take into account the advantages of undamped vibration isolator and linear damping vibration isolator, which can not only effectively reduce the resonance peak value of the system, but also ensure the excellent vibration isolation performance in the high frequency region. It provides a theoretical basis for the design of new nonlinear vibration isolators.