Resonance-free vibration isolator of model GWF dissipates vibrating energy by means of Coulomb-damping and elastic deformation, and it is widely used in vibration isolation for electronic equipment due to no harmonic peaks. Based on analysis of theoretical model, the unlock frequency and vibration isolation transmissibility for the GWF vibration isolator were obtained, the correctness of the theory was verified and an experimental and theory basis for selecting appropriate stiffness and friction force were provided.