Objectives  Studying the influence of the system parameters of a quasi-zero stiffness isolator on vibration isolation performance can provide a key direction for the application of quasi-zero stiffness isolation in vibration isolation systems.

  Methods  Based on a double layer vibration isolation system consisting of linear isolation and quasi-zero stiffness isolation, as well as an equivalent linear vibration isolation system with two degrees of freedom, dynamic models are separately established. Moreover, the average method is applied to derive the power transfer rate under the condition of two harmonic force excitation systems. It is proven that the double layer vibration isolation system has better vibration isolation performance than the equivalent linear vibration isolation system with two degrees of freedom, and a method for enhancing the vibration isolation effect of the double layer vibration isolation system is proposed.

  Results  The results show that the power transfer rate of the double layer vibration isolation system is greater than 1 in the second order resonance frequency, which means that it has the effect of vibration isolation in the vicinity of resonance frequencies of the second order, which overcomes the shortcomings of the freedom linear vibration isolation system with two degrees of freedom.

  Conclusions  The double layer vibration isolation system can improve vibration isolation performance by appropriately reducing the damping ratio, mass ratio and stiffness ratio, giving it better low frequency vibration isolation performance than the equivalent linear vibration isolation system.